Windows of Linux

[Jangita]

Hello all,

Im about to start a service that will be doing about 50 transactions a 
day so will grow to quite a large size.

i was wondering without considering network security, which backend 
would be the best? windows or linux - we have 500 different clients who 
*might* all connect at the same time, in addition to the sheer size the 
database will grow to...