Hello again 
There is one major difference between these two models and they are different products as the main section of the product name is different as opposed to just a single character on the end. Taking a look at the official product pages and specifications.....
VCT-50AV - http://www.sony.co.uk/product/cac-tripods/vct-50av
VCT-60AV - http://www.sony.co.uk/product/cac-tripods/vct-60av
..... the difference is that while the VCT-50AV has a height range of 460mm-1170mm with three stages that the legs can extend, the VCT-60AV has a range of 480mm-1465mm and has four stages of leg extension as well as a crank for extra control over lowering and raising on the tripod. Furthermore, for your choice of the camera (the HDR-PJ260VE), this is only listed as a compatible model with the VCT-50AV and not the higher range model.
Thanks,
Simon