The difference between the 30g -> 55g will be how fast you think you can type vs. mistakes.
55g has a snappier lift off, so it's closer to say a BS board in that it'll give you a bit of a rebound onto the next key.
30g will be really really light, which will make it very mistake pron until you get used to it.
Now, I haven't really seen that many 55g and 30g Topres in Japan outside Cleverly in Akihabara. Usually I see variable weight boards, and occasionally 45g uniform.
Now variable weight, is a bit of a different beast, as it tries to get the nice balance (45g for stronger fingers) for all fingers. This is definitely the most common one.