Beginners slr? Nikon or canon?

So i'm looking for a beginners slr for somewhere around $700
i have my eye set on the nikon d3100, but i was wondering if there was a canon that was better?
i'm mostly interested in taking pictures with long exposure

Really either brand is fine. The D3100 should suit you well. Canon has the rebel t2i and t1i for around the same on amazon which has slightly more Megapixels but what really matters is what lens you stick on the end.

The D3100 is great if you've never used an SLR before as it has an Intruction mode on there that can help guide you on picking the right settings for your camera which won't make it perfect but wil give you and idea of how to use in it the manual modes which is how dSLRs were meant to be used.

In this range both Canon and Nikon are good. The D3100 is a pretty good camera but I would go for the D7000 myself because I want more advance features. Try both the entry level Nikon and Canon DSLRs in a store and see which one appeals more to you. Be sure to check the online reviews as well because it will help you to make your decision.