I think I've figured this out. The '85 244 with the low low miles is the one. Here's my thinking:

1. The 940 is worth little enough that any significant repairs will likely sink the boat - that is, next time it needs anything major, in order to keep peace at home it will probably be sold off as a fixer for a very low price.
2. The 244 is special. Clean and straight, pretty and peppy. Needs nothing and shouldn't need anything for many years at the rate I drive.
3. The 940 is a "used car"; that's a good thing but does color the trade study a bit, at least from the standpoint of which car is attractive. That is, the 940 is entirely unremarkable.
4. The 244 is (maybe) a "best in show" candidate, at least among Volvo heads.

Thanks to all of you who provided input on this question. If anybody has more to say on the subject I'm still listening.
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'85 240 DL with 37K miles, '94 940 with 191K, 40 linear feet of vintage jazz, r'&'b, funk and soul