I'm guessing you mean AMDtuning at Lakeside.
Here's what I can say......both have a good forum reputation,and that's one of the most important things a tuner can have,as you know people here will post up the good,the bad and the downright ugly about anything.
I don't have any experience of R-Tech,so I'll leave that to someone else,but AMDTuning have served me very well over quite a few years now,and built my car from a stock vehicle to Stg4 with Revo software,including top and bottom end rebuilds,to a standard that another tuner described as a very good spec indeed.
I now need not only AMDTuning for my local work,but also Storm Developments for ECU and other work,so I can recommend both wholeheartedly.