RNV
I've never heard of anyone having a leak where I fly.
The remote needle valve is safer, no doubt.
Some allow you to position the needle in such a way that is exits the cowl on the left, right, top or bottom of the airplane.
Some are hollow and have a set screw so that you can insert a piece of wire to extend them.
There is some lag when you adjust the needle valve. You turn the needle and have to wait a moment for the change.
Why don't all engines have them? I believe most O.S. engines have them. I may get bashed here, but if you buy a O.S. clones to save a little money keep in mind the manufacturer has to cut costs somwhere so you can save a few bucks...
JMHO,
-Bob George