Gonna be the contrarian here... sort of
What’s the bonus, ballpark? 50 or 75k, or more like 20? What is it after tax? I’ve seen a few spots of seniority make a heck of a difference - furlough is the obvious one - but usually once you settle into the middle of the list in a base people overhype the importance of a couple of numbers difference. For example once you can hold a solid line, bidding technique can give one a lot of virtual seniority. But if your goal early on is to bid over to a tough to get aircraft of base, it can matter a lot.
People mentioned a few things you’d lose - like a year of profit sharing, perhaps 100 seniority numbers or so.
If you’ve got serious cash coming your way and plan a long career here maybe roll the dice - time value of money and all that. Otherwise I’d agree with everyone else here, take that first possible class!!