I probably should not answer as that is dangerously close to an aesthetics question (short version is we call me to make things a) work or b) figure out how they work but never to make them look pretty).
Still the late GBA/early DS era and the flash carts that resulted was an odd one- proper GBA carts (like the EZ2 and EZ3) were still fairly available, indeed it is presumably why we got the likes of the EZ4 lite compact, supercard rumble and m3 professional that sacrificed most GBA ability to have DS code run, and as GBA emulation had always been good things wavered a bit, doubly so once the nopass and DS slot stuff took off. Looking back there were some interesting, for want of a better term, fads where fairly trivial (at least once cheats were available for all) things became deciding points for flash carts.
For what it is worth I reckon I should have picked up more proper GBA carts and Another World has expressed similar sentiments at various points as frankly most did not expect GBA carts to drop off as quickly as they did (many would argue the main reason the EZ4 is still around is because of something of a concerted effort on the part of several sites and individuals to have the EZTeam stop pondering making another batch and actually doing it).
As for still finding an EZ4- it is getting harder and mainly because the older shops that carry the stock are slowly giving up but I imagine you will still be able to pick one up for a while as it seems most would be flash cart owners have been trained by the DS and consoles to expect things for the price of a couple of pizzas. P.S. as for the EZ2 the 512Mbit versions are one of the most highly sought after carts out there and though it may not be drag and drop virtual machines have great passthrough options and most halfway modern machines can run a very cut down version of XP at the cost of a couple of gigs of hard drive space- I just checked and my IE8 virtual machine which is kind of cut down XP sits at 2.19 gigs.
