Slight correction
GDP = grandaddy purple. It's very similar, if not the same as purple urkle. It is not within the 'family' of mendo purps (fast growing sativa type) but it does share the same color and similar beginnings of origin - The NorCal/Oregon area. A lot of people call Urkle many names. Mendo purps is one of the many incorrect names given to her.
Whether or not she's 'stronger' than master or og kinda depends on your body chemistry, and how she was grown. Urkle/GDP, in my personal experience, is a 10+ week plant. She's stronger at 10+ weeks but everybody pulls her at 7-9 weeks. A couple of runs back i checked her trichs at 9 weeks and they were still clear. I pulled her at 9 weeks this time, and yup, she was weaker than my last batch that was pulled at 10+