I'll chime in. I've built 2 systems and can at least speak to some of these from personal experience. You can see them both in this pic.
First, let me say that I think your categories aren't really how you want to think about the differences. You mixing apples and oranges.
The different things to consider are:
stand: 3-tier vs 2-tier vs single-tier
mash heating techniques: HERMS vs RIMS vs direct-fired vs steam
You can build a system with any combination of stand design and mash heating system. For example, there's no reason why you can't have a 2-tier stand that uses HERMS to maintain temps. I've seen some great systems that do just this.
: From a cost standpoint, I don't think there's much difference. The materials required in increasing order are probably: single-tier/brew tree, 2-tier, step-type 3-tier. I don't think you can argue that one is more versatile than another. They can all be used to do anything you want a stand to do.
Pros: Simplicity. No pump required (unless you're going to recirculate). Gravity does the work.
Cons: MLT and HLT are up high. You have to use ladders/step ladders for access. You may have to lift heavy/hot stuff over your head. If you're doing any kind of recirculation, you have to have a pump anyway, so why not use a 1- or 2-tier design?
Pros: Lower than a 3-tier. You can fly sparge with a single pump.
Cons: At least 1 pump required. MLT or HLT may still require a ladder for access. More lifting than single-tier. If you batch sparge, the single pump is sufficient, so why not build a single-tier?
Pros: Everything is low and accessible. No high lifting.
Cons: 1 pump required if batch sparging, 2 if fly sparging.
Mash heating techniques
: I honestly believe there's not much difference in the techniques. They all achieve the same result. They can all be automated. The only real difference I see is difficulty.
Pros: Simplest technique (IMHO). Doesn't require any extra equipment if you stir while heating. Direct-fire + recirculation is fast and easy.
Cons: More danger of scorching mash/wort, especially if the recirculation stops.
Pros: Relatively simple complexity. No danger of scorching the wort.
Cons: Requires a pump and heat exchanger coil. More difficult to use if you want to maintain temps and then raise temps.
Pros: Easily maintains and raises temps.
Cons: More complex to build than previous methods. More difficult to operate manually - I think these systems are typically automated. Heating element can possibly scorch/caramelize wort.
Pros: Most effecient method for heating the mash. Gently heats, so no danger of scorching mash/wort.
Cons: Most difficult type of system to build (IMHO).
Hope that helps. Hopefully some others will chime in.