No - I would keep with Delta if you fly them on occasion - their miles don't expire (though do devalue even more quickly than UA/AA) and they have an occasional 5-10k domestic Y sale so you could probably find some value in them eventually.
Otherwise I would credit to SQ since SQ earns at 100% for UA (so useful if you aren't going for status and have a flight where 100% > your RDM multiplier) and because they are a transfer partner of all major currencies so you can transfer in to get some useful award level and redeem for UA, SQ, or other *A.