Big law associate considering switching to a regional firm?

Hi Lawyertalk, hoping for some professional development advice or insight on anything I may be missing here.

I’m a fourth year associate at a big law firm in an environmental practice group. My firm’s environmental group has consistently been losing people, and the only other person in my office is retiring this year. I currently and would in the future be working exclusively with partners in other offices. Not only that, but the work has really dried up and I’ve been way underbilling. I just had my mid year review and got only positive feedback, didn’t even mention hours, but I’d be surprised if I have a long term future at this firm given how slow I have been over the last year. Hours minimum is 1700 at this firm, but bonus is 2050. I have struggled to get enough work the entire time I’ve been at this firm, and it has caused me a lot of stress. Also, due to certain partners leaving the firm, we no longer do much of the type of work I like doing.

New job would be at a regional firm, between 60-80 attorneys across five offices. It pays about 5/6 what I make in big law (so a notable pay cut, but still well-paid). Their primary and biggest practice is environmental law. Their environmental group has also been consistently growing. They also do entirely the type of law that I want to be doing. Hours would be 1850 to be eligible for promotion and 1900 for bonus. I feel that my likelihood to potentially get promoted to partner and bring in clients would be significantly better at this firm. I also liked all the people I interviewed with.

I am thinking I will take the midsize firm job. Is there anything I should be taking into consideration here? Anything I am missing?