well, actually this question can have a million different answers, there will be no ending to as why people choose 256 or 128,
the most important thing is you decide what you want the space for, if you dont mind on using the 2.0 USB for external storage transfer which is obviously slower than the SSD, then 128 is good, save the cost as well to buy your external HD
as for me, i will be going for 256 because:
-Boot Camp for Windows, at least 80gb + EvE Online
-Movies/Anime/Music for traveling entertainment, at least 100gb for it
that leaves me roughly 70gb ( Including Lion OSX ) which then i only have around 50ish gb clear storage
for me, that is pretty tight, with 128, i will never have the space to do this
so yeah
the most important thing is you decide what you want the space for, if you dont mind on using the 2.0 USB for external storage transfer which is obviously slower than the SSD, then 128 is good, save the cost as well to buy your external HD
as for me, i will be going for 256 because:
-Boot Camp for Windows, at least 80gb + EvE Online
-Movies/Anime/Music for traveling entertainment, at least 100gb for it
that leaves me roughly 70gb ( Including Lion OSX ) which then i only have around 50ish gb clear storage
for me, that is pretty tight, with 128, i will never have the space to do this
so yeah