edwardb gave a good basic explanation of the benefits of the three-link over the four-link. So here's my thoughts that may help you decide on which way to go.

Don't get too hung up on which one is supposed to be the best as this is very subjective and highly dependent on the intended use of the vehicle and your ability to tune it. The best designed suspension will only achieve its potential when someone with the knowledge sets it up properly. In the hands of a novice a suspension with lots of adjustability may lead to some interesting and nasty handling characteristics so the "keep it simple" approach may be better for most folks. The simplest suspension FFR sells for the 33HR is the triangulated four-link and there is really not much to adjust or mess up.

The three-link may be an improvement but it is still seriously lacking in design as it carries over the inefficient triangulated lower control arm design of the four-link and has little adjustability for folks that know how to tune a suspension. Then there's that banana bracket that folks seem to have trouble with. But you probably can't mess this one up too much as there is really not much adjustment you can make. Ride height is probably the one adjustment most will make and not understand how it affects handling and the other suspension dynamics. Suspensions are a system and when you make an adjustment as simple as ride height it affects other areas.

Then there's the IRS option and a good one it is. If I wasn't planning to drag race mine I'd have opted for the IRS and it would have saved me a ton of modification work. It's not so complicated that a good alignment shop would have trouble setting it up and if you decide to learn about suspension design and set-up down the road it would make a good base in which to tinker with as you learn.

But all three of the suspension choices offered will give you a car that handles much better than the typical family sedan even if it's not set-up ideally. However, once you decide on a design you should consider that permanent. Unless you have a large checkbook or serious fabrication skills you will have to live with your choice.