I will be moving up from 25NL to 50NL sometime soon. I have heard that 50NL games are acutally tougher than 100NL Does Party have the weakest opponents at 50NL or is there a site with weaker apponents that would warrent me leaving party?

50 is a lot easier than 100 at least for me. Not sure why.

Tribeca is the current BTP destination of choice for weakest players around. But they're pretty weak all over the place at 50NL.

it just depends what you mean by 'weak'

B2B and Tribeca have very very bad push muppets/calling stations
Stars, Prima and UB are more likely to be 'weak' in the sense of making too many lay-downs to pressure.

The thing is to find a site you are comfortable at and just be happy to rake in the $$ there - changing from one sort of site to another - eg from Tribeca to UB is likely to get you burned until you readjust (as I found out to the tune of 2.5 buy-ins earlier this week!)