To each their I suppose, but...

I was on a similar plan three years ago: BOS to DCA on Sunday night and then DCA to BOS on Friday afternoon. I'm still down in DC probably two to three times a month, so my regularity on this Shuttle has fortunately decreased exponentially. I mention this history because my recent experience is less voluminous than in the past, but I don't think things have changed that much. Suffice it to say: AVOID JetBlue!

B6's schedule is less frequent and the lack of interline agreement was particularly problematic especially during the winter months. IME, B6 could never seem to board a flight on time and the boarding process in general was and still is chaotic. If upgrades are your thing, even with the A320s, I rarely if ever missed an upgrade as EXP back then and still rarely do. It's one of the few flights I'll book Y instead of F. The embraers make the UG even easier. Finally, just thinking of worst case scenarios: it is helpful to have access to the AC Angels during IRROPS (and they were/are much more helpful than the B6 Moscaic line). If B6 cancels, the chances of getting reaccommodated are slim to nill.

The only plus with B6 that I can offer is the same day confirmed change with Mosaic, which only requires a spend similar to that of AA Plat. If you're buying your own tickets instead of your employer, you can book the cheapest flight of the day and then call that day (i.e. 00:01) with B6 and switch to flight you want. Typically, there was always a seat or two.

AA's service is actually pretty good in general on the Shuttle. Many of the more seasoned FAs work these flights and when you're on them enough, they get to know your drink of choice and it's nice to see familiar faces. Also you're start to recognize passengers who are also on the same schedule.

Don't envy this, but best of luck!