Thanks for all the comments. I think it's a tricky situation, especially without any reads.
I played around with ranges a bit to get a better idea and came up with the following possible range for UTG:
22+,A9s+,KJs+,QJs,ATo+,KQo (open for discussion)
Based on this range, we now have three options available:
1) Fold - low variance option but pretty tight 6-handed and we might miss out on some value
2) Call - here we have to adjust UTG's range for the flop. Maybe something like 77+,AJs+,AQo+. The question is how much we still want to invest post-flop and which board is good for us. If we have an overpair, UTG might bet for value or contibet. Do we call either way and fold to a second bet on the turn? As soon as one OC hits, it gets ugly. Even if he checks and we do as well to keep the pot small, we might let him draw for free. I think calling leads to some very difficult spots post-flop where we can lose even more. Worst option in my book.
3) Shove - most variance-heavy option but if we assume the above range of ~12% open raise and think that he will only call with premium hands like QQ+,AQs+,AKo (3%) we gain quite a bit through our fold equity. That means he folds 75% of the time and only calls us in 25% of the cases where we still have 38% with our JJ against his tighter range. I am excluding MP here since the important part is the battle of the two big stacks.
I did shove in-game and I think based on the calculation in point 3 a shove is +EV. But I can also see a fold here. I personally don't like calling since it can get pretty ugly post-flop. I'm happy that some people find the hand interesting and wouldn't mind some more opinions on it. 
