Robb makes a good point.
However,,, many have found that a new base pin isn't necessary,,, as their handgun never jumps forward under recoil. The factory pin is just fine. The pin jumping forward is usually the first reason folks look for a Belt Mtn. The base pin latch assy is a good idea as well, as it can solve the jumping by a factory pin.
Heavy recoiling guns suffer this more than milder ones.
Now, some of the Belt Mtn pins come with a locking set screw to apply locking tension to the underside of the bbl.
Also, sometimes the pins are a few thousands oversized & must be fitted. Belt Mtn sends instructions on how to fit one.
And,,, to address the #5 style,,, it is a different look, AND is functional. Many of us like that,,, especially when adding a custom touch to our guns.
But on the other side,,, you have to look at how a mass produced Ruger handgun is built. There are some variable tolerances that are in these guns. Since the barrels & cylinders are not line bored like a custom built one may be, there has to be a SLIGHT amount of play in the cylinder to allow for alignment of things when the bullet transitions from the cylinder to the bbl. (Excessive play is not a good thing.) There have been some cases where a gun was made tighter by a Belt Mtn pin, or other mods to where accuracy suffered, and spitting of lead increased. Not too many cases,,, but enough to warrant studying before making changes.
Many of us like & use Belt Mtn pins w/o any ill effects. But occasionally it could be a step backwards. They are a quality product, and can help many guns tighten up enough to make an improvement too.
So,,, in general,,, we usually ask; "Why do you NEED one?" If you are having base pin jump,,, then by all means,, it will help. Next, we ask; "Do you just want one for extra insurance or looks?" Many follow this train of thought. And some look at the #5 style & feel it is just a better look AND function.
I own some myself, and have never had any of mine decrease the accuracy or cause any problems.