Originally Posted by LUTNIT
As long as your hopup is set right, both will have the same range, the 0.25's will have a tighter grouping at any range, the only advantage of 0.20's is they will get there faster but such a small difference in travel time is pretty much meaningless at the ranges airsoft is played at.
When I purchased my TM SIG 552 SEALs gun it came with a bag of 200 .25g BB's. I just tried them out for the first time today and you were right about the tighter grouping. I had to adjust my hop-up a little differently though cause like 75% of the settings I tried were totally inaccurate. But once I found that right setting, it was so accurate. When I was using .20g BB's, even with the right hop-up setting at least 2 out of 4 shots were inaccurate. Mind you, that I'm shooting my gun indoors and about 20 feet away from the target box. So the results would probably be different if I were outdoors and further away from my target.