+ they *supposedly* keep the saddle in place better
- horses with lots of movement in their shoulders hate them (or at least mine did) because it snugs up the front of the saddle a bit more than regular billets
- flocking has to be adjusted more often due to the smoosh factor
I usually have the point billets removed, and have another standard billet installed.
You want your billets to drop down and be perpendicular to the ground. A point billet can help with that. Much of it depends on the design of the saddle, how forward the flap is, and where your horse's girth groove is. Big shoulders and a well-sprung barrel are also indicators that a point billet will be helpful.
As an aside, my Amerigo CC has four billets. The one closest to the front would act similar to a point billet. At first glance it looks like it's farther back than a point billet would be but it's an illusion because of the forward flap. In relation to the actual tree points, it's pretty close.
Interestingly, on my dressage saddle, the point billet is a good thing. On my CC, which has much shorter tree points, if I use that forward-most billet, my saddle slips. So there are plenty of factors that go into billet placement on each horse and with each saddle.
Saddles tend to slide forward on my mare so we had a point billet replace the regular old billets, and it worked like a charm. It seemed no matter how well a saddle was flocked to her and fit her on the ground, when she moved it slid up because of where her girth groove is (very close to her armpits if you may).
There was no problem switching the billets and it was a relatively cheap procedure, I would imagine you could switch it back to the other way if you wanted without much difficulty.
A point billet works great on my wide-shouldered Arab. It helps line up the billets with his forward girth groove, and the saddle is very stable. Same saddle, same flocking, but regular billets meant the saddle was constantly pulled forward.
I had the billets changed on my saddle - it was relatively inexpensive, something like $50.
An anatomic girth like County Logic is another option if your horse has a forward girth groove.