+1 I also prefer gzipped .d64's although not all tools handle them transparently. Coming to think of it, there should be one that extracts .d64.gz with a single file in them. Shouldn't be too hard to write.
c1541 image.d64.gz -read '*'
6. When I see PRG file in CSDB database, I immediately know this is tape game.
When we have games uploaded in D64 format (like CSDB asks for users), I don't know immediately if particular game is disk or tape game, and I need to check Gamebase 64. 7. When you have game uploaded in ZIP format, I also don't know if this game is disk or tape game, and I need to check Gamebase 64.
I'm not really familiar with GB64, but do they really keep track of all cracks of games and whether they where cracked from tape or disk?