R6KII + EF135/2+1.4xTCII or R6MKIII + EF 135/2 only?

Which of the above has more cropping power and or more resolution? I am going to the Aussie Open and I cannot take any lens longer than 200mm. I am thinking of using my R6MKII and the ever dependable EF 135/2 L. I have the 1.4XTCII too. I already shot tennis with this combo (with and without the 1.4xTC) using the electronic shutter @ 1/1600 sec. and some @ 1/2000 sec. and I haven't seen any elongated racquets or oblong tennis balls. I am open to trading in my R6MKII if the MKIII will be...