I may be in the minority here, but I find Sony NP-F / L-mount battery powering a very attractive feature. My Zoom F6 runs 6 condenser mics for a very long time with a 6800 mAh battery, and is one of the best things about that unit.
As others have stated, the big unknown about the PR-4 and PR-6 is preamp quality.
Zoom's F-series preamps and Tascam's higher-end units offer performance plenty good enough for the prosumer market. If you need higher quality in a field recorder, you go to Sound Devices or the other serious pro brands.