Personally I don’t think you can go wrong either way. Different cultivars behave differently within the same grass type. For instance, Bewitched is a KBG that does very well in the shade while other KBG cultivars may or may not. Within KBG you have some cultivars that are more disease resistant, some green up earlier, some are better in sun or shade, some are darker or lighter than others, etc. Same with TTTF. One factor to consider is whether the all fescue or all KBG sod is one cultivar or a blend of different seeds within the category of fescue or KBG. Monostands (I.e., one cultivar type or KBG or one of TTTF) can look beautiful but a monostand can be more susceptible to a disease or fungus. In the end, I’d be fine with a KBG blend of various KBG cultivars or a mix of KBG and TTTF. If you want to really get into it google NTEP trials undertaken at the Rutgers sites and they go into great detail about different grasses and how they perform in our area. That’s if you really want to go nuts about it, though.