Which is the best move?

My employer wants me to stay on in a new position they are creating. I have a degree in math and statistics and want to do analytical type of work (I was doing admin/clerical work). They don't have anyone currently doing statistical work but would love to have me around for various projects. I've gotten used to the place, and I love my hours too as I get to come in early morning and leave by early afternoon. It's boring at times but everyone gets along pretty good and it works well with my part-time graduate program. But I am also being considered for an entry level financial analyst position in another department. That's the field I have been extremely interested in since undergraduate school. This would probably be more challenging and open more doors. But the hours are later and I'd probably have to work overtime as finance work usually has to be completed each day. My studies could be affected. What would you do?