Hmmm, well I've tried a lot of them and am even expecting a shipment of the 'biodegradable' diapers soon. Honestly though, there's not really a big difference with 7th Generation or anyones with similar claims. From what I've been able to tell, they're unbleached so use slightly less chemicals to make the diapers (I could go on about how this is really a pretty minor difference and there's even a lawsuit going on over this claim, but it's a little complex and my post is already long enough). But everything else is pretty much the same, the paper inside, the plastic outside, the absorbant gel inside etc... They're ever-so-slightly better but nothing really drastic in my opinion. The Tushies don't even have the unbleached advantage, the only difference is that their diapers use some cotton for absorbancy (instead of only paper, they have paper & cotton inside), which I'm not even sure is a good ecological step and they don't use the absorbant gel, which some are uncomfortable with in regular diapers. The fact that they're pure white and don't contain that gel can be good for newborns though, since it's very easy to tell when they've peed (contrary to all other disposables).
The Nature Boy & Girl diapers are the 'biodegradable' ones (the outer plastic is actually made from corn). They have the potential of being pretty great but the problem lies in actually putting that potential to work. You can't compost the poopy ones (or at least it's very controversial because you need a really 'hot' compost to safely kill the bacteria) and there's some question as to how well a large amount of this plastic would truly degrade in compost and what effect it would have on the compost. Oh, and if you just throw them out (which I'm sure is what most people do) then they likely don't degrade a whole lot better than regular disposables. In a plastic bag inside a oxygen-deprived landfill is just a very poor environment for *anything* to decompose.
The only 'disposable' option that has any true advantage are G diapers. The absorbant insert can be flushed or composted. Flushing still uses about the same amount of water as cloth and if your municipality ends up putting solid waste in the landfill they're there's only a minimal gain in landfill space. But composting makes a significant difference and is very doable, especially if you only use them occasionally. I would even recomend using the flushable inserts inside any velcro wrap you already have, in my opinion this is easier and won't leak (not that Gs leak for everyone, but some people have to fiddle a lot to get a good leakproof fit).
Anyway, that's my 2 cents. Probably more than you wanted to know (and I could even go on some more, I've researched this a fair amount) I'm sure. I guess what I'm saying is that disposables are disposables and although some are a smidge better than others (and I can certainly appreciate wanting to at least support a company that is making an effort for the environement) there's really no significant difference in them. Gdiapers being the only ones with a significant advantage (if composted especially).