Jim, since my only experience is with the Torchmate, that's all I'll be able to comment on.
I bought my TM2 "Bolt-Together" Table in 08. It literally was "bolt-together".. probably took about 1/2 day total to get it together and everything hooked up. The instructions for everything were spread out over a few different manuals so it was a little confusing at first. However, I think TM has come a long way with their "downloadable" manuals.
Since owning the table, the only things I've had to replace were the bronze nut on the ATHC (nut wore the threads completely out at the 4yr mark), and one of the bearings on the gantry (I actually just moved the frozen bearing outboard where it rarely contacts the rail).
Other than that, this thing has been carefree for 5yrs. As for usage, the table probably gets about 8-10hrs of actual cutting per week.. sometimes more.. sometimes less.
Good call on the Hypertherm. I love my 1250 (predecessor to the PM85). With my PM85 Retrofit Torch, it's not uncommon to see upwards of 1000 pierces from a set of consumables. Cut quality remains relatively unchanged from first pierce to last pierce. The other benefit of the larger cutter, is the Duty Cycle. I've cut an entire sheet of 1/2" at 60amps without hitting the duty cycle.
Water table is a good call. Love mine. Best "upgrade" I've done since buying the table.
In a shop environment, consider an Auto Torch Height Controller a "must have". That's what allows you to hit "Start" and then walk away.
If you plan to load with a Forklift, look into the TM3 with the dropped rail. It'll allow you to pick up a sheet with the forklift and lay it on the table's slats without fear of dinging up your rails. If using a crane to load sheets either a TM2 or TM3 will work fine.. I think the TM2 is a little cheaper.
I would say get at least a 4x8 table. Something that will take full sheets. If you have the space and $$$, a 5x10 would be even better. A 5x10 will allow more creative nesting and will allow you to throw on different thicknesses of steel at the same time.
Leave access to all 4 sides of the table. It'll make it much easier to retrieve parts.
Don't go any deeper on the water table than is necessary. Mine is only 4" deep.. and it's plenty. At 4", I can still get my fingers down to the bottom to fish out small parts that occasionally fall in.
I did my slats at 1.5" spacing. While some may consider that small, I love the fact that 90% of my parts stay put. Very few "tip-ups". Very few parts fall thru the slats. The nice thing about parts staying put, is that you don't have to worry about "dinging" an edge with the arc as the part falls away while the torch is still firing.
Use a "Remote Controller" for the system. I bought TM's "Remote Pendant" system which allows me to stand at the table and run basic functions.. jogging the torch around, resetting the program, zeroing, starting/stopping the program..etc. There are some guys who've even adapted a wireless controller to their Torchmates.
Along with the Remote Control, get a "Laser Crosshair" for the torch. It'll make precise positioning easier.
With Stepper Motors, it's easy to use "hard stops" to run up against.. for zeroing the system out. You run to hard zero, move to the starting point (make note of the X,Y coordinate), and start cutting. If you "lose position" for some reason (run over slag, hit a tip-up..etc.), you can always go back to hard zero and regain your position. That can save you a bunch of material, especially when cutting an array that consists of lots of closely nested parts.
As always Jim, feel free to hit me up anytime if you need anything.