1. Poloniex is a real-time exchange like Bitstamp, whereas 100bit.co.in is direct trading exchange like LocalBitcoins, though it allows Alt coin trading as well.
2. 100bit.co.in does not require your fund to stay deposited with the site. So, in case of any security breach, there is no chance that your fund will get affected, unless you have a live trade exactly at that time.
3. 100bit.co.in trading fee is same for all volume of trade. It is 0.001 BTC flat for each trade.
4. 100bit.co.in is an invitation only exchange. It requires a referral & 0.01 BTC to join 100bit.co.in. An user earns 0.003 BTC from each referral joining.