Fred - both units are actually quite good. The Primaluna will sound more articulate than the Modwright LS36.5, even with tube rolling, and the Modwright will deliver with more musicality and soul.
If you are only being offered the 36.5 as stock and not the two chassis LS 36.5 DM, the Primaluna may be the better bet performance-wise. I believe Dan Wright still offers an upgrade to the LS36.5 DM, but I’m not sure if the price is still $2500 or if it has gone up over the years. Regardless, the upgrade is a substantial difference and worth considering if you truly want an endgame preamp. I owned the LS36.5 for many years and it was very hard for me to let go of. I demoed it against dozens of other units, and I even preferred it over an Audio Research Ref 6. I only let it go when I moved to an entire T+A HV series stack (before becoming a T+A dealer).
The PL EVO 400 is a very good unit despite my praise for the Modwright. That said, be prepared to invest extra in good tubes for it to get it to sound its best.