nolimits

Engines yes but trans depends. Manual yes, PDK no. The PDK is good to lesser whp on a road course but at high levels (stage 4, 750ish flywheel +) you need Dodson clutches etc. Otherwise some overheating and slipping. Cars are very well built for track out of the box compared to most.

A/S

I have a 991.1 Turbo S and 991.1 GT3 RS. With the RS, I ran stock exhaust, Sharkwerks center bypass, FabSpeed headers and side delete muffler + stock Ti center, and now stock headers/center muffler and side delete by FVD (my favorite sound setup but a little loud when I don't want to be loud, so next step is a side-bypass with valve control like FabSpeed, TPC or soon Dundon).

991.1 Turbo S, I ran stock exhaust, Tubi muffler + Tubi sport cats, Kline Inconel header + Kline catless race exhaust, Kline headers + Tubi exhaust + stock cats.

Best sound on Turbo S, Kline inconel headers + Kline catless exhaust. Sound was better than all my RS sounds from multiple configurations, except my current RS setup or the RS with FabSpeed catless long tube headers.

On a racetrack (road course of any kind) , my Turbo S beats my RS. For driving around town, my Turbo S is much better than my RS. I like them both. My TTS has a tune, some small suspension upgrades and that's it.

If I had to choose one, I would keep the GT3 RS because it's rare, I see GT3s and Turbos everywhere, but rarely a GT3 RS. Rarity is a fun factor for me, but if you don't count on that, then Turbo S is my choice. I like rare cars (cars that no one, or few people have, or cars barely seen out).

But I would never trade a 991 Turbo S for a plain GT3 (non-RS).

To truly enjoy a GT3/GT3RS you need to rev it past 7k rpm, 1st gear goes quick, 2nd gear is short, 3rd gear and up is where you can enjoy this engine, but at 7k rpm in 3rd gear you're approaching 100mph, so there is no fun in the GT3/GT3RS unless on a racetrack or European/South-American roads.

The Turbo S is fun at 10mph, 20mph, 30mph, it is so quick and traction gifted, than coasting off of a stop sign it pulls away quickly.

Don't read the hype, I have thousands of miles on both, and Turbo S wins.

Papa Fittig

Great points Steve Cole and A/S.
While I fully agree that the TTS is superior in many ways, to answer OP's question I think GT3 demand is driven by the fact that it is an apogee of NA engine lineup. Availability of proper 6sp MT helps too.
Coming from NA/MT world many, myself included, consider the GT3 being the best option for a driver's street legal practical car which at the same time is very capable on the track.

Cargt63

Cancel the Flabspeed exhaust. Go with the Kline setup (Inconel, 100 cell HJS cats, equal lenght Inconel headers) through Sam Ahdoot. yes it is $12,000 but my Turbo S screams like a GT3, is faster and has zero drone! I am just a happy customer.