i just bought a bunch of ram and have all these different sized sticks around so i did some tinkering in win98SE...
128MB is good, but adding more definitely shows a noticeable increase in performance..
192MB was better, but i still noticed more improvement at 224MB..
256MB made no noticeable difference from 224MB...this is with the conservativeswapfileusage=1 line in the system.ini and teh vcache settings manually set with a fixed virtual memory swap file of 100MB...
thus, i'd say that buying one 256mb dimm (or two 128) would be the best, even under win98se..it makes more of a difference in win2k.
the best improvement is caching, obviously...if u open something, close it, and access it later, it opens it a lot quicker w/ 256mb over 128mb...
plus it's so damn cheap!...i just 128mb pc133 spectek for $53 canadian...