Oh, I am definitely going to try both of them but only after I try the rest of the lenses, because after hauling those big, fat babies around, on tripod or not, I might need some sick days. After that, who knows.
I didn't like the 500/8 Nikkor, but there are different versions of it and there should be one that's better than others (one of the more recent ones I think). I have no idea which version I tried.
I just realized that there is a Praktica Super TL there too, I just didn't bring it over. That might work better than Zenit TTL, until I get my hands on a Spotmatic or find the adapter for Rolleiflex. Praktica has a somewhat better/brighter finder than the Zenit, if my memory serves.