I went through the Chailly Mahler 5 yesterday, and I greatly prefer it to the Jansons. For one thing, it's better recorded. The all important bass drum - really crucial in M5 - is much more present on the Chailly. Yes, Chailly also slows down at rehearsal figure 32 in the finale (where there's no indication to do so), but to a much lesser extent than Jansons. Also, Chailly doesn't stretch out the reprise of the big brass chorale tune at the "Pesante" marking, anywhere to the extent that Jansons does. Back in the second movement, while Jansons starts out a tad faster, Chailly doesn't slow down the slightest at the 20th bar. Jansons slows down quite a bit there; and again, there's no indication to do so. Chailly strikes me as a more steady and solid throughout, less episodic. In the middle movement scherzo, the solo horn sounds more forward on the Chailly. For some reason, the (French)horn playing just sounds better on the Chailly in general.
I would like the Jansons better if, 1) it were better recorded; 2) Jansons didn't slow down shortly after the start of the 2nd movement; 3) if he hadn't stretched out the big brass chorale theme the first time through, near the end of the 2nd movement; 4) if the horn playing were "great" in the scherzo; and if he hadn't made such a huge ritard at figure 32 in the finale, robbing the ending of energy BEFORE the return of his greatly protracted, main chorale tune (at the Pesante marking).