It seems like a furlough resulting from a lower seniority number would be a lot easier to take if you had the full retirement check coming in each month. If you leave early you have to consider the possibility of a sickness or injury that could result in you losing your medical. Then there is the possibility of your airline merging and the two pilot groups having to merge their seniority lists. You are leaving pretty much a sure thing to work for a company that, in all likelihood, filed for bankruptcy just to avoid promised pensions and benefits for an earlier group of employees.

This. It's the best of both worlds.
Get out, get a seniority number. Then see if you can work out getting the last 2.5 years in the reserves or by being called back to active duty. You will have a seniority number at your airline that will continue to build while getting your military retirement.

There are exceptions to every rule of thumb, not sure why you felt the need to point out the obvious. *shrug* I was chief of XP in my last assignment and the MAJCOM chief insisted everybody take some kind of BS oath of honesty prior to doing inspections. Not sure how XP got recruited into IG but he wanted me doing inspections instead of flying. I refused to take any oaths and he found somebody else, I got to fly. Where there's a will there's a way.