I am a huge fan of four fletch. For the longest time I shot 4 5" shields, but have recently switched to 4 4" shields. I think the 4 inch offers the same stability without compromising performance at longer distances.
The benefits as I see it are first and formost improved stability after the shot. I have slow motion videos of arrows grossly over spined being straightened up within 5 yards by four big feathers. On the flip side of the coin, you do lose speed as distance increases (think fluflu). I also like the benefit of not needing a cock feather to index in the times that I need to get an arrow on the string in a hurry (mostly small game).
I like 90 degree orientation, as it simplifies things. I haven't yet had any trouble with feather clearance on multiple different setups that couldn't be solved with a little quick nock tuning.
Many will argue that a well tuned setup doesn't need four feathers, and they would be correct. I'm a fanatical arrow tuner and I still sleep better on the night before a hunt knowing that fourth feather helps.
Just my two cents, hope it helped.
Jake