You don't say what your needs are.
The Acekard supports SDHC while the R4 doesn't, but is going to cost you over twice as much. The Acekard can also update it's cheats over WiFi, that's only of use to to if you want to regularly update the cheat database.
The R4 team is dead, all the R4's you see on sale are clones, of those you want the 1:1 clone because it's the only one which can run Wood.
ShopTemp sell these 1:1's for $6. The Acekard team is still alive, but you wouldn't know it. Meaning that currently both the Acekard and R4 are dependant on 3rd party software, both of which are still active. ShopTemp are selling the
Acekard for $14.95
ShopTemp ship from HK and are trustworth as they are affialted with GBAtemp, you can select DHL/UPS shipping if you want in a hurry. Otherwise you can buy from SimplyMods or LeetMod which are based in the US.
If you want to have a good comparsion, I've written both a
Wood R4 guide and an
Acekard Akaio guide.
Might be worth checking the contacts on your R4. You can try placing a piece of paper behind the sticker as you insert it. If that doesn't work, open the shell up and place a piece of Tape underneath the PCB where the contacts are.
If you can't open the shell up (should just be a screw on the back) you can try my sliding a piece of paper underneath the contacts trick
It's from My Acekard guide.
It's probably worth yo u getting another R4 anyway in case it fails, they are only $6 and are handy for a spare.