The "from which builder should I buy" question has come up many times. Posed here - it's a difficult one to get answered objectively. Those who already own a Replica Speedster might have an understandable bias toward the manufacturer who built their car - self-validation, and all that.
However, there are some general "givens" that I think most all of us would agree upon. At the risk of bringing down a thousand "flames," I'll try to list a few (as I see them).
Intermeccanica builds the best replicars. Period. They may be more expensive than the rest, but they are "automobiles," not kitcars and the difference in quality is justifiably reflected in the price tag.
Beck and Thunder Ranch are building their replicas on tube chassis (as opposed to shortened VW pans). This is widely acknowledged as a stronger basis on which to build a car. Each of these companies is worth investigating by contacting their customers through the directory on this website.
Specialty Auto Works (SAW) is building Subaru (water-cooled) powered Speedsters and Roadsters. Their extremely long build-times are an impediment to many, but their modern engine technology application is a lure to those who don't wish to mess with VW AC engines and all that they entail.
JPS Motorsports (who built two cars for me) and Vintage Speedsters are the original kitcar manufacturers. Vintage is a high-volume shop, able to turn out a brand new basic Speedster within two weeks. JPS is generally more detail oriented and will custom-build to a customer's specs, but the process will take longer than VS.
There are additional builders, but those are the major players. Most of the other folks marketing Speedster Replicas are simply reselling cars from existing builders (almost always Vintage Speedsters, but some others, too).
Here are a few questions worth answering before you buy a replica:
Is authenticity important to you? Do you want your car to replicate a German-built Speedster as much as possible? Or is that not a concern?
Is performance a consideration? Do you want your car to be faster than a 70-HP VW engine? (By the way, it doesn't necessarily need to be.)
How important are the details, like "fit & finish?" Generally, some builders are much better at the little things than others. If you don't notice these things, then why pay for them?
Finally, and probably most importantly, do you want a new car, or could you be happy with a low-mileage used car? Buying used is not only less expensive, it's a safer way to introduce yourself to the hobby. Should you become smitten with replicas, like most of the folks here, you can always have a "dream car" designed and built to your specs later, selling your starter car to someone else coming up the food chain.
Learn all you can about these cars. Try to see examples from each builder if you can. But, at the very least, contact some owners via e-mail and get the direct answers to your specific questions before you write the check. Visit all the builders' websites. They're linked on the "Makers" tab on this site.
(The opinions stated above are mine and may not represent anyone else's on this website, but I've tried to be as objective as possible - that's the disclaimer.)
Good luck.