Asked myself the same question when I researched this a few years ago and opted for flat nose.
My coach is 101inches wide which means that the distance from the hitch ball to either rear corner of the coach is approx 50 inches. If the trailer tongue is 51inches or more, then no risk of hitting both the trailer box and motorhome corners. We're assuming flat and level terrain. There remains however the tongue structure itself compared to the v nose structure and this is where the flat nose trailer will allow a slightly sharper turning radius. On most trailers, the tongue structure is welded to the trailer frame structure which is in my case 18 inches narrower than the trailer box walls thus allowing an additional 9 inches of turning clearance on each side. Whereas on all of the V nose trailers that I saw, the box walls of the V portion extend from the full width of the trailer towards the coupler thus eliminating that 9inch clearance.
On three occasions, I ended up lightly scratching the corners of my coach because of excessively sharp turns while backing up (all because of my inexperience) which necessitated minor cosmetic repairs to the coach. Had I owned a V nose, there would have been much more damage to the coach and to the trailer also.
Another consideration is the tongue jack. My coach rear cap extends back over the hitch by a few inches which brought the tongue jack motor too close to the coach for my liking. Because of the open space in front , I was able to relocate the jack further back. Couldn't have done that as easily with a V nose.
Good luck with your shopping.
Gary & Johanne
2005 Mandalay 40E & 26ft Enclosed Car Hauler