Well, maybe I can contribute something here… Tony is right that the regular design has worked well for a long time and is still going strong. Both designs are easy to read the angles, due to the shape of the vane and the bi colored ball for direction. Both have the same sq inches of the Hi-vis material. The main advantage to the flat tops is to be able to stack more flags in your scope. Guys using the raised reticle scopes like them for this reason. The ball is at the top of the flag so even if you overlap them half way you can still see the ball at the top of the flag. Guys with regular reticles can usually get one or
maybe two more flags than usual in their scope at 200 yds depending on the situation. If you have your new March turned up on 80X forget it!)
You gain about 1.5” per flag. So what that means is if you put your furthest flag right under the target, each successive flag you gain 1.5” over where you could set the regular design flags. So if you use say 6 flags at 200, you gain 9” in height for you flag closest to you. I other words the flags can be up closer to where the bullet is. If you overlap them it would be more. On very low ranges, you can get away with less offsetting of the flags (for visibility) because of this. Another thing, the FTs stack nice around berms or other trouble spots. (You can come up closer to the front and back side of the berm due to their shorter height.)
There are some disadvantages to the FTs. They are a little more awkward to handle due to everything being down from the pivot. Storage is a little trickier… with the regular flags guys often just put a 2x2 block in the bottom of their storage box with .75” holes drilled to set their pivots in. It works well. The FTs you can’t easily do that because the vane is down from the pivot. You can use finger adjustable pivots and turn the vane over when you store them (a little more hassle) or you need to put the block up high in your box from side to side so that the vanes will hang down when the pivots are in the holes of the block. With the XL FTs, the pivot is closer to the vane, and can create clearance problems if you have large knobs sticking out on your stands in some situations. (the FT vane travels around the stand) Another thing with the FTs is you lose a little tail length. (with the vane being down instead of up) In situations where you need a very short flag set up this can leave you with not much tail. I try to help with this by putting two anchor points on the FTs. One at the bottom, and one close to the top. That way if you have a short flag situation you can use the top tail anchor point. (I prefer the bottom anchor point in all other situations)
You might also consider your shooting style also. If you like to stay on that scope a lot like a lot of guys do these days, maybe the FTs might help with that. I am a heads up shooter, so either works just fine for me. I am more likely to be concerned with having enough of the XLs out there so my tired old eyes can see them!