IBTD. The single port 1300 "F" engine is one of my favourites. Sure, it does lack the punch of a 1600, especially a single port 1600 -- but it's sweet, reliable, and reasonably fast in a '60s Bug. A better 1200 in every respect, and very notably faster than one, without being costlier (which the 1600s are).
The dual port 1300 "AB" engine is not as nice, but it still is an okay engine, and even when burdened with a heavy Super Beetle still notably faster than a 1200 Bug. It's just not worth it -- if you're going to put up with a dual port and the leaky intake manifolds and higher revs and worse mileage they come with, you might as well go 1600 and have something to show for it. ;-)
Just MHO of course, YMMV.
Airhowlingly yours, Erik.