When I upgraded back in 2019 I had the same dilemma. Ultimately I ended up going 737 for the following reasons:
1) I had lots of previous time in it from the right seat;
2) It went to Hawaii and the Bus didn’t;
3) It was one less thing to learn brand new while I was perfecting my Captain-ness

All that aside I don’t think you can go wrong either way. While I’ve never flown the Bus everyone I know that has gone from Boeing to the Bus has enjoyed it. They’ll teach you everything at TK and like anything new it takes a bit of experience for it all to click but when it does everyone seems to love it. Even doing some of the smaller “regional” layovers on the 737 proved to be really fun. There’s always going to be a great spot for some food and an adult beverage if you look and have time. That’s one of the great benefits of going to the left seat, you’ll always get to fly with your favorite Captain and you get to set the tone for the trip.