A good "entry level" front sway bar is a 3/8" so-called "stock" bar for a '66 - '77 Beetle sedan with a beam front end. Since the car is lowered from the stock height as a speedster, the 3/8" bar seems to work quite well for many people, giving improved cornering control while not making the ride too harsh.
If you have a swing arm rear suspension, this should be accompanied by a rear camber compensator (others on here can offer suggestions on which is best).
If your car is an IRS rear, then you could consider a rear sway bar, not a camber compensator - that's for swingers.
The next step up would be to the 3/4" front sway bar. It will be a bit harsher ride than the 3/8" but honestly, many people don't notice the difference in ride. What will be different is that the car will corner flatter when pushed than with the 3/8" bar and that will be noticeable. I've often thought that a 5/8" front bar would be ideal for a Speedster as the compromise between ride harshness and flat cornering, but I don't know if anyone offers one.
Full disclosure; I have an IRS car and started with just the front, Sway Away 3/4" bar and it flattened things out a lot in the hard corners. Someone gave me a new sway-away rear 3/4" bar that wouldn't work on their swing arm car (you oldies might remember Andreas, who left MIT to go teach back home in Germany) and I installed that, too. That made the car corner even flatter than before and I have never been able to break the rear tires loose on track days, even when I was specifically trying to see how far I could push it, both at Roebling Roads, SC and Thompson Raceway, CT. Those rear tires were 225/40's which have been replaced with 205/50's but I have no track time on the new tires.
I have zero experience with EMPI sway bars. All I've ever had or installed for others were from Sway-Away which are great quality and (more importantly) they fit without fuss.
Let's see what others think.....