Well, I too, have both carts and it's kind of hard to say which one is obviously better because to be honest, both of them have their advantages and both have disadvantages.
Cyclo comes with more features. You'll have Real Time Save, and a few other things like In Game Guide and Slow Mo. But these aren't really that necessary if you are just looking to play a few games here and there. Cyclo's support has also gone done a notch or so from before. They used to update frequently and introduce new features (like Battery Saver Option, and a few other improvements) and constantly update firmware for game fixes. They even promised a new GUI overhaul and initial gave the idea that a Cyclo for the DSi would be coming out. But they didn't deliver either. Yet. They don't update firmware/features as much anymore. And the cost is pretty much overpriced.
Acekard2 on the other hand, doesn't have those features, but the GUI is fast, responsive and very slick. The support isn't great because AK2 doesn't really update firmware often, but the unofficial firmware, AKAIO, updates often and is very clean cut. For example, Normatt came out with a Spirit Tracks (Zelda) fix for AKAIO faster than any other patches and Cyclo hasn't even come out with firmware to fix. And for $13 (or so), the Acekard2 is a really good deal. You could get at least 3 Acekards for the price of one Cyclo.
And there you have it! Sorry it's kind of long. But really, it's an subjective issue over which cart is better so you should decide for yourself!