We have a lot of WTO live tool holders somewhere around 35 or 40, and we have had pretty good experiences with them we have not had a standard speed tool require a rebuild. We also have about 30 Eppinger holders for our Doosan machines. We have a few WTO holders north of 400 hours. We have a few Heimatec holders and a few MD Tooling holders(we just got and have not run yet, but MD made much more affordable geared up tools for Doosan machines- for some reason the other brand BMT-55's are 40% or more expensive).
In our experience the WTO's are higher quality than Eppinger in terms of rigidity and cutting quality. The Eppinger tools can't really be driven as hard because the collet nuts will loosen and allow the tools to come out [maybe the nuts have a more coarse thread]. We teflon tape Eppinger nuts for that reason which is a pain in the ass. That may not be a problem if you use the preciflex system, but those accessories aren't really cost effective, and sometimes don't have enough reach to get to centerlines anyway.
If you compare std 1:1 tools from Eppinger and WTO, the WTO tools cut a little better. If you compare 3:1's from Heimatech to WTO 3:1s , I believe the WTO's cut a little better and we've had good experiences with their non coolant through 3:1 tools.
Operators dislike Eppinger because they don't have a one hand wrench, and WTO does have a one hand wrench. WTO tool changes are faster than Eppinger if you run standard nuts. A couple of our guys cut themselves pretty decently changing tools on Eppingers, and I have not seen anyone cut changing tools with WTO. I think operator acceptance is important because I want the guys to be happy, and because people with cut hands work slower and get paid the same. People running CNC machines don't really need distractions like workplace injuries to increase the risk of driving a machine while distracted and causing something expensive to happen.
We use a lot of Tekniks 3/4" shank ER speed nut extensions and 3/4" ER25 special collets to get tools over our QG65 compact chucks, and we use some of the Rego Fix Recool adaptors. The Regofix recool adaptors are really nice, I only wish the coolant lines and flush discs and nozzles were less expensive, but that's pretty much the whole Rego brand- nothing is really priced to sell. They put a lot of geometry into Rego flush nozzles that doesn't matter- curved conical ID's when flat with a hole would work- we cut down the flush nozzles a lot because the tool hangouts need to be short to cut well. The Rego coolant lines and fittings only last through the job, so they are kind of a consumable.