About external/regular hard drive disc

Currently this is my system:
2.1GHZ E6300(the old one not the Pentium) processor.
Already sad me current HDD(does 50-60MB/s write/read and 18m/s latency).
palit 9800GT 512MB(can run every game today on high/med and AA in 1280*1024)
17" lg screen.
1GB RAM 667MHZ.
As i sad I'm using SATA with me internal drive(have eSATA also, so external drive with esata would be great).
my budget is 80-100$.
not quite sure if to buy the 2.5inch/3.5inch or 3.5inch internal(thats why i made this thread).
here is my thoughts:
2.5inch:
Pros:I want to get games and movies throw my friends and i dont want to carry power adapter
Cons:expansive and slow.
3.5inch:
Pros:i want to somehow carry info through my friends.
Cons:quite slow.
3.5 inch internal:
Prosamn fast and cheap.
Cons:i couldn't exchange data with my friends.
btw, 500GB will do the job, i don't need better.(nor the super-fast ssd/15k)

Didn't know that you had eSATA, wasn't in the original post.

If that's the case then if you want to be able to take data/movies etc to friends places then go with the external. On your system, hooked up by eSATA it will be just as fast as being plugged in internally.

3.5" 500GB external eSATA from tigerdirect.com - $75
http://www.tigerdirect.com/applica [...] atId=2429]

Any 2.5" drive is $90+ and won't be eSATA (that I know of)

If you get an external drive with BOTH USB2 and eSATA connection options (these are very common) you can use the eSATA mode at home which is almost the same as an internal SATA drive and won't slow down your gaming. But when you go to a friend's house to exchange data etc, you can use the USB2 ports because almost ALL your friends will have that. It just would not be as fast for actually playing the game at your friend's house. Get an enclosre and drive spearately and assemble, or buy complete, whichever suits you. Buy the 3½" HDD size - better capacity and lower price - and take the power brick with you - it's pretty small!