MM IBD vs Top AM Fixed Income

Background: about to finish up an MSF at a semi-target. Quantitative undergrad at non-target with coursework in stats, finance, and data science. I'm solid quantitatively but not enough to pursue the quant route. My two offers are a top MM IB (think HL, WB, Jefferies) doing M&A in a sector that I have decent interest in but has an introverted culture which I don't love and the other is a Fixed Income Analyst role at a top asset manager known for FI with a diverse mandate and responsibilities (treasuries to high-yield securities with exposure to research and portfolio management, it is an active investing role that works directly with the PM). Both are in NYC and pay well. Good performers at the AM will have mobility to try out other asset classes.  

Intentionally, I'm leaving out my "long-term" goals because I'm just fascinated by a lot of things. I have enjoyed my FI coursework / prep for the interviews and thought my previous IB internship was interesting work but I'm not necessarily cut for the hours (I could do it for 2 years tops). What are your thoughts on where you would want to start your career or other considerations I should evaluate?