A couple of other benefits of T-bars which may not be obvious.

1) They reduce the unsprung weight of the car since the T-Bar itself is entirely sprung. Normally half of a coil spring is considered to be unsprung.

2) The packaging benefits may be beyond the golf bag scenario. When you use Coil Springs, you need to reinforce the chassis spring perches (usually high up on the chassis) as well as suspension mounting points. This can involve some significant material. With T-Bars, you often do not need any additional spring perch reinforcement since the T-bar works through the existing suspension mountings and the loads are spread out across the T-bar mounts. That reinforcement that you do need can often be mounted very low in the chassis.

Keep in mind that Porsche has never paid much attention to "What everyone else was doing". That is why we own air-cooled, rear-engined, T-Bar suspended cars. Porsche was/is certainly known for sticking with a concept and refining it for years if not decades. I believe that Michael Cotton once pointed out something to the affect of Porsche having an almost fanatical dedication to a design concept. The fact that everyone else was using coil springs doesn't make coils better, it just meant that a lot of the other car companies are risk averse techonology followers. Coil Springs are no perfect solution either -- each concept has trade-off's.

I'm sure that Porsche chose T-Bars because they offered the compromise that Porsche wanted. Coil springs are compromised in regards to unsprung weight, packaging and travel. T-bars are compromised in regards to the range of pressures that will fit in a certain application.

You pay your money and work with your decision.