Get the SanDisk microSD Express 512GB. It's fast, and on long writes, like moving a big game onto the card, SanDisk rates it not to drop below 220 MB/s. None of the other three gives a floor in MB/s.
The ROG Xbox Ally X20 has one card slot, and it's a microSD Express card reader, so it takes Express cards like these. Each of the four is here for one thing it does best.
At a Glance#
Best overall : SanDisk microSD Express 512GB View on Amazon
Best with a drive-health check : Samsung P9 Express 512GB
Best 1TB : Lexar PLAY PRO 1TB
Best 256GB : PNY microSD Express 256GB
Key Highlights:
- The X20's one card slot is a microSD Express card reader, and it reads ordinary UHS-I cards too
- SanDisk: up to 880 MB/s read, and rated not to drop below 220 MB/s on long writes
- Samsung: Samsung Magician checks from a PC or Mac that the card is genuine and keeps track of its health
- Lexar: the 1TB card, with up to 900MB/s read
- PNY: 256GB, up to 890MB/s read, and an A1 rating for running games from the card
Who this comparison is for#
- Want a card rated not to drop below 220 MB/s on long writes? Get the SanDisk.
- Want to check from a PC or Mac that your card is genuine and healthy? Get the Samsung.
- Need the most room on top of the X20's built-in 1TB NVMe drive? Get the Lexar.
- Happy with 256GB? Get the PNY.
How we picked#
- These are all microSD Express cards, the kind the X20's slot is made for.
- Each one earns its place with one thing: a floor in MB/s for long writes, health checks, the most space or a 256GB size.
- We haven't tried them in an X20 ourselves, and price didn't decide the order.
- Speeds are the makers' ratings, and real speed depends on the device and how you use it. That goes for SanDisk's 220 MB/s floor too.
The four cards side by side#
| Card | Capacity | Rated read | Minimum write | Warranty | Buy |
|---|---|---|---|---|---|
| SanDisk microSD Express 512GB | 512 GB | Up to 880 MB/s | 220 MB/s on long writes, in SanDisk's own testing | Limited lifetime, 30 years in some countries | View on Amazon |
| Samsung P9 Express 512GB | 512 GB | Up to 800 MB/s | No MB/s figure | 3 years | View on Amazon |
| Lexar PLAY PRO 1TB | 1 TB | Up to 900MB/s | V30 mark, no MB/s figure | Limited lifetime, 10 years in some countries | View on Amazon |
| PNY microSD Express 256GB | 256 GB | Up to 890MB/s | V30 mark, no MB/s figure | Lifetime limited | View on Amazon |
SanDisk microSD Express 512GB — Best overall#
This is the card to get for the X20. It reads at up to 880 MB/s and writes at up to 650 MB/s. On long writes, like copying a big game onto the card, SanDisk rates it not to drop below 220 MB/s. That's SanDisk's own test result, and your device and how you use the card can make it slower than that. None of the other three gives a floor in MB/s.
Its ThermAdapt technology helps keep the card from overheating, and SanDisk backs it with a limited lifetime warranty. In Germany, Canada and places that don't recognize lifetime warranties, that becomes 30 years.
One thing to know: SanDisk sells this card for one particular console and lists no other device for it. It's still a microSD Express card, the format the X20's slot takes.
Key Specs
Capacity : 512 GB
Rated read : up to 880 MB/s
Rated write : up to 650 MB/s
Minimum sustained write : 220 MB/s
Speed conditions : Compatible device required to reach these speeds, based on internal testing, can be lower depending on the device and how it's used
Thermal : ThermAdapt, helps keep card temperatures within operating limits
Warranty : Limited lifetime, a 30-year warranty in Germany, Canada and regions not recognizing lifetime warranty
Model Number : SDSQXFN-512G-GR6ZN
Bottom line. Fast, with a rated floor for long writes, and the one to get.
Samsung P9 Express 512GB — Best with a drive-health check#
Get the Samsung if you want to keep an eye on the card. Samsung Magician Software checks that the card is genuine and tracks its drive health, on Windows and macOS.
It's the slowest reader of the four on paper, at up to 800 MB/s on a PCIe test board, and Samsung doesn't give a write speed. The warranty is shorter too, three years against lifetime for the others.
Key Specs
Capacity : 512 GB
Rated read : up to 800 MB/s
Speed conditions : PCIe test board, actual speeds may vary
Software : Samsung Magician, Windows 10 and higher, or macOS High Sierra (10.13) and higher
Thermal : Dynamic Thermal Guard, helps reduce overheating
Warranty : 3-Year Limited Warranty
Model Number : MB-MK512T/AM
Bottom line. Get it if checking the card's health from a PC or Mac matters more to you than a lifetime warranty.
Lexar PLAY PRO 1TB — Best 1TB#
Get the Lexar if you want the most space. It's the only 1TB card here. It reads at up to 900MB/s, and writes at up to 600MB/s when paired with Lexar's own microSD Express card reader. Lexar got those speeds in its internal testing, and only a microSD Express host device can reach them.
Put it in an older UHS-I or UHS-II device and it still works, at UHS-I speeds. You also get a limited lifetime warranty and the Lexar Recovery Tool for getting back deleted files.
Key Specs
Capacity : 1 TB
Rated read : up to 900MB/s
Rated write : up to 600MB/s, with the Lexar microSD Express card reader
Lower figures Lexar also lists, for all three sizes : Up to 205MB/s read, 140MB/s write speeds
Video speed class : V30
Warranty : Limited lifetime, limited to 10 years from purchase in Germany and regions not recognizing lifetime warranty
Model Number : LMSXPS0001T-BNNNU
Bottom line. The card to get if space matters most.
PNY microSD Express 256GB — Best 256GB#
Get the PNY if 256GB is enough. It reads at up to 890MB/s and writes at up to 750MB/s over PCIe Gen 3x1, and its A1 Application Performance rating lets you run gaming apps straight from the card.
Got an older device with a UHS-I or UHS-II slot? It works there too, at UHS-I speeds. It has a lifetime limited warranty, and you can get a trial of PNY Photo Recovery software for getting back lost photos.
Key Specs
Capacity : 256 GB
Rated read : up to 890MB/s
Rated write : up to 750MB/s
Speed conditions : Needs a compatible host device fast enough to reach these speeds
Thermal : adaptive thermal technology
Interface : PCIe Gen 3x1
Video speed class : V30
Warranty : Lifetime limited, plus a PNY Photo Recovery trial
Model Number : P-SDU256P31880EXP-GE
Bottom line. The 256GB card, fast and ready to run games from.
Which one should you buy?#
Get the SanDisk microSD Express 512GB for the ROG Xbox Ally X20: it reads at up to 880 MB/s, and SanDisk rates it not to drop below 220 MB/s on long writes, a floor the other three don't give in MB/s.
Get the SanDisk unless one thing already decides it for you. It's fast, it has a rated floor for long writes, and it comes with a limited lifetime warranty. View on Amazon
Get the Samsung if you want Samsung Magician keeping an eye on the card from a PC or Mac, and the Lexar if you want 1TB. Get the PNY if 256GB is enough.
Our recommendation: buy the SanDisk microSD Express 512GB, unless the most space, the health checks or a 256GB card is what you came for.
FAQ#
Does the ROG Xbox Ally X20 take ordinary microSD cards?
Yes. The slot is a microSD Express card reader built to SD v8.0 over PCIe Gen4 x1, and it also supports UHS-I with DDR200 mode, so a regular UHS-I card you already own will work. ASUS doesn't list UHS-II for it.
Do any of these cards say they work with the ROG Xbox Ally X20?
Not by name. They're microSD Express cards, and the X20's slot is a microSD Express card reader, so the format matches.
What warranty does each card carry?
Three of them, the SanDisk, the Lexar and the PNY, come with a limited lifetime warranty, though in some countries SanDisk caps it at 30 years and Lexar at 10. The Samsung's warranty is three years.