Should I get a Slot 1 cart?

I want to dump my Max Media Dock on my brother (he never shares anyways) and pick up a new cart. I was going to settle for GBA only homebrew that way I don't have to buy any type of pass but these new Slot 1 options sound so cool and are much more useful. I was thinking Supercard.

The problem is, when I visited the MaxConsole forums, I was hit by a bunch of Supercard Slot 1 issues. Apparently some of the carts don't work and compatibility is low. Now I am thinking M3 or R4. I hear they are both the same but which one is the better buy?

Also, where's a good, trustworthy place to find deals on these devices? Same question for SD cards.

Thanks.

EDIT: I remember reading of poor homebrew compatibility. Will I be able to run NESDS, DSDOOM, PicoDrive, and ImageView? I use these the most.

I suggest the R4 and from www.mopchipstore.com the ground shipping, which was 6 bucks, shipped in 3 days. It was a total 51 dollars shipped. It can run NesDS, I'm running it right now and its great. If you have any sav files R4 can convert that so you won't have to start all over again. I totally recommend it, and it comes with a lot of goodies.

Thanks.

Dude your info was totaly wrong. SC DS and DS-LINK are the best followed by the M3 they are all proven companys Supercard and M3. They actually haqve the best compatibility. I know i buy all the new crap that comes out. and i will tell you thoes two that you just mentioned are the worst. plus look at how freaquent the supercard and ds-link make updates right now everything i have tested is compatible. but then again is your choise.

i heard that the R4 is made by the M3 team.

Not only that, the R4 and M3 Simply are actually identical to one another with only slight modifications. The M3 team explained that they sell the one product while their factory sells the other product. This explanation really doesn't make much sense to me, but it at least confirms that the two devices are identical and are made by the same basic people.