Just for interest sakes, did a quick & dirty test... here's the results:
AT&T - 4.0.0.17
All Applications:
TOTAL FREE: 3828772
After Removing Applications:
BrickBreaker (48K)
DOD Root Certificates (28K)
Help (85K)
English Language UK Support (6K)
TTY Support (2K)
Password Keeper (31K)
TOTAL FREE: 4172632
Rogers - 3.7.1.41
Factory setup
TOTAL FREE: 5840356
For Browsing... I honestly think it's the javascript that kills performance. For JS to work, it has to load onto the BB then run so you get a double-whammy (download first, then execute). Not sure about the browsers datastore... I would think it's static-sized and replaces content as needed.
Personally never really put any thought into how many messages I can store... more so because I actually delete mine on a regular basis , I don't think I've kept a message longer than 4 days (delete prior is my fav function
).