I did test by search similar keywords on both of them and found that MSN and Live search results are almost completely different. It seems that Live.com brought more accurate results and something make me think Live using some of algorithm based on current Google algorithm. Why do they have to use different algorithm on both?
The reason for the difference is that the live.com beta has the adult content filter set to "strict," while search.msn.com uses the moderate setting. Once the beta actually offers a control to let users change the setting, it will produce results identical to search.msn.com. That should be soon. But it really is the same search engine behind both of them.