Westley375,
I have shot guns with both types of forends and for me, I like the semi beavertail, I hope this is not seen as some kind of compromise. If I had to choose one of the other of the two types you mentioned, I would take the full beavertail. I have heard this arguement about splinter versus beavertail till I'm sick of hearing it. I think that the main reason the Brits put splinter forends on their rifles is because that's also the type they were putting on their shotguns at the time. Lets face the fact too, that they were in the business to make money,and the splinter forend is dead easy to make and fit compared to a nice beavertail.
There is much to be said for the lining up of the hands on the same plane, IF we are talking about instinctive shotgunning at flying game using a straight hand english stock, but I don't feel that that has anything to do with a well aimed shot from a double rifle with a pistol grip on it.
I have heard all the hokum about the stress and strain on the forarm if it was made as a beavertail, but I have yet to hear of one that actually failed in the field. My best advice to you is to get the one that feels best and shoots best for you, no matter what these guys tell you. It's your gun, and this is not a popularity contest, shoot what works best for you. Bob