The Suby is a whole 'nuther beast.
How? Well, to start, you have 30% more horsepower on tap from the get-go, BUT you also have a LOT more torque (the power you feel) that comes on a lot lower in the RPM range than a typical aircooled engine. The power curve is much flatter on a Suby so you can get by with a higher ratio (lower number) ring and pinion set and take advantage of more power at any rpm setting.
If you had the typical Suby 2.5, properly carbureted (non-fuel injection) and "stock" VW gearing in your transaxle (gear 1-4), I would expect that you, and the engine, would be quite happy with a 3:42 rear ratio or something like that. Heck, the Suby expects to be turning something like 2,200 rpm at 70mph so the VW gearing might fit nicely as it would be a tad higher, like 2,500-2,800 rpm or so at 70mph, if you kept the stock .89 fourth gear on a VW transaxle.
On the other side of the coin, let's say that you're running a 2,110 VW type 1 aircooled engine. First, your "sweet spot" in engine rpms is 3,000-ish for optimum cooling, unlike the Suby that doesn't care about cooling rpms since it's water cooled. Second, you have a much lumpier torque curve - more like the shape of Mount Monadnock (look it up...It's lumpy) - that brings the torque on above 3,000 rpm, unlike that Suby that has decent torque around 1,500 rpm and up. Lastly, the lower numerical ratio in the rear end (higher gearing) the more you're making the engine work and the less power you will feel - it's all leverage. If you gear for highway travel then acceleration (in any gear) suffers. If you gear for acceleration then your top end or cruising speed suffers. Original Speedsters were geared for racing and acceleration. They were all done around 100mph, but they could get there quickly - they were quick but not especially fast. You have to decide what you want to do with the car and gear for that. Life is a compromise.......