I have been reading on this site for some time, but today is the first time I decided to post up.
I want to say first off, so no-one gets the wrong idea, I am a Pro-Drive Owner and a Pro-Drive Dealer. I respect all the other opinions posted on here and guys like HH and UT are honest folks, regardless of their opinions.
I have now run all the major shorttails, finally ran the GD last week, ran a GT a few months ago, ran the hypers last year and the hyper sport a few weeks ago. I have run PD motors since they first came out.
Here is my take on all of them.
The Hypers are good motors, had a few more problems being new to the market, however they took good care of folks. They are offering a couple of clutch options this year, just be sure you get the one that meets your needs. The auto clutch is cool, but you have to be careful not to overheat the clutch at slow speeds. The balanced hypers are more difficult to drive and they do ride up more in the junk (compared to the sport models, GT or PD), but are still considerably better then a longtail. They are fast with the larger motors they had out last year. The new sport is very much like the Gator-Tail in design and handling, better then the balanced hyper. They are smooth machines. The 35 hyper sport is impressive.
The GD surface drive is a heavy built machine, I think only second to the PD in "toughness". It is fast and with the drive angle is similar to the PD in "bite" in the grass and junk. It still is a little "pushy" in the corners, similar to the balanced hypers of 04. It is still a balanced drive with no neutral, but is seems to be great option.
The GT is the first of the belt driven models developed. It is a powerful unit and seems to be the fastest stoke model HP for HP. Again, the shorter shaft makes it handle better then the others balanced models. They have reworked there reverse option for this year and are offering a conventional reverse unit. I have not seen this model yet. It is a great machine and a great company.
The Pro-Drive was the first and has the longest development history. Unlike the others it is gear driven. it also has the shortest drive and the most weight back over the prop. This makes it the easiest of the four to drive in rough water, mud and shallow water and in hard cornering. The minimal profile in the water means less tiller push in corners. It will hit thing harder then the others, so that is one plus for the more balanced drives, however the PD is over built to take the punishment. The PD 32 is running very close to the other 31-35 HP motors as far as speed and seems to be a bit better with load. I do believe that the angled drive of the PD is one of the big differences. This can be argued by others, but I have run all four in similar situations and the PD was the easiest to get out of the grass, shallow mud and really thick stuff. The PD reverse (which turns the lower unit 180 degrees) is the king in the shallows, it will get you out of stuff no other can, this is no bs, it is amazing to see.
In summary, they are all great motors, it just depends on what you want and what best meets your needs. Any one of these motors will do circles around a long-tail on 99% of the situations you put them in. I would suggest you get as much information as you can, drive them if you can and make an informed decision based on your needs.
Again, other may not agree with me and thats okay. I for one have taken the time to try them all, granted I am a dealer and I don't think I am without bias for a minute. But I try to be straight forward with folks. It is hard to really compare all four without driving each one. They all have their advantages and strengths.
Thanks, hope this is helpful, or at least gets you asking more questions and doing more research as you look at all your options.