In looking at transfers from hotel points to airline miles, it might be better to avoid transferring into DL.

More generally, a big advantage of these programs can be to transfer into a program in which you don't earn many miles, so that you have more flexibility for award flights--for example, DL doesn't offer one way awards (except for the same number of miles as a RT), so having some miles in UA can be very useful and similarly for destinations that aren't served well or are tough for awards on SkyTeam versus *A, although the cost can be taking such award flights without status.