Unless you have a 3G and either the 4G or 5G, I don't think you need to worry whether or not the sound is better in the 3G compared to the other two. The better question (which you did ask) is whether unmodded 3G is better than modded 3G, and to that, I'd have to go with modded. Sadly, this conclusion isn't based on experience but rather from transference. Going from small, "low quality" caps to larger, "high quality" caps seems to work well with the other diyMods, so why not with this one? I've AB-ed between 22uF and 47uF in my 4G, and by far I prefer the latter. I've tried it with 1.0uF VitQs and 220uF Nichicon PWs, and the setup I prefer the most is the 47uF BGs for their balance of convenience and sound quality. I am working on a 3G right now, so I can give you quick impressions. Really, there isn't any guarantee that you'll like the diyMod over the stock version, but at least you'll have a chance to roll different caps to suit your style. You only have to go as far as the first page to see all the different kinds of setups we have in the way of diyMods.
Hope that answers your question. Don't hesitate to prod any further.