I match my ballistics to my game and expected shot distance, so I use both depending on conditions and how I'm hunting. Even my version of slow and heavy is 300yd capable.. just in case. But, IMHO, to me at least, the platform and how it's setup is almost more important than the cartridge.
For instance, my .350RM in a 20" barrel launches a 225grn at 2730 FPS, it's basically got the trajectory of a 30-06 180 grn. Using the MPBR concept a 239yd zero gives it a MPBR of 280yds on a 280yds for a 6" TGT. With it's 200yd zero it's only 8" of drop at 300 and 23" at 400 (30-06 being 7.9" and 22.8). Even IF I bump up to a 250grn at 2500, it's still a 300yd capably cartridge/combo. When I hunted elk in timber, I just dropped the 250s in, the POA VS POI was moot on a target that size at those distances. Once I developed my 225 NP load, the 250s fell by the wayside.
IF I was putting something together for an elusive "all around" 300yd rifle for whitetail, I'd probably just re-build my .260RM and use 130ABs, or go with a 7-08 (anything 308 based really). IF I knew however that the majority of my time would be spent still hunting, or doing drives in wooded terrain, then yes I'd probably go for a .338Fderal or a .358Win in a compact format with a lower powered scope. I would love to find either in a 760-7600 set up for a "timber rifle". IMHO, both the 338F and .358Win are 300yd cartridges, which would cover clear cuts etc.
For presentations/shots that may not be perfect, I error on the side of slow(er) and heavy(er).