Your choice, of course, but IMO better to hit DM, then look at a challenge. Staying at DL Plat, you would be (at best) only Plat on UA and only the Gold equivalent with AA.

If you reach DM with DL, more possibilities open up. First, you have SC membership, a nice bennie even if not flying DL. You could even gift GM to someone else if you like. But maybe most important, higher DL status means higher match/challenge status. If still an option (seems to come and go), go for 1K on UA or ExPlat on AA.

I suppose there is also US but sorry, don't follow that airline at all.