Delta, at least Miser attempted to answer the OP's question, you didn't even bother to try -_-
Although I don't own an iEDGE, from what I hear its firmware simply just isn't as good as AKAIO's. The EDGE team releases compatibility updates on occasion, but they do so usually long after (usually a week) AKAIO has already received updates. I also believe that AKAIO has a slightly nicer/quicker/user-friendly interface than the EDGE's
Functionality-wise, both carts are basically barebones kits that only play roms. However, The iEDGE has a bootstrap firmware that can be updated any DS/DSi regardless of firmware, while the Acekard2i's bootstrap can only be updated on on a DS that is NOT a 1.4U DSi. I doubt any of these apply to you since I am assuming you own a DS lite.
One of the bigger advantages the iEDGE has over the Acekard2i is build quality. Some Acekard2i's suffer from contact issues after a couple of months of usage. On the other hand, the iEDGE has basically the best build quality out of any DSi cart on the market.
Overall, I think the Acekard2i is better cart than the iEDGE, simply because of AKAIO, but it isn't better by that big of a margin.
Just a word of warning: AKAIO and Wood R4 are basically freaking identical. If you are buying an Acekard expecting to get something new, you aren't. The only features you gain from going from an R4 to an Acekard is DSi/SDHC compatibility like Miser said. With Wood R4, the R4 is actually one of the best carts on the market right now for compatibility, so don't be fooled by its old age. Maybe you should invest in a bunch of 2GB microSD's instead?