Could be one brand is just converting better then the other and nothing more, that happens quite often. I would not call this shaving at all. I have some brands where I get 100 downloaders out of them I will get 40 new registering players and of that 40 I will get 15 to 20 dep players BUT at another brand same results and can only get 5 depositing players.
Hope that helped 
Shaving is a hard thing to prove but that happens more so when you have consistently over a long period of time a earned a certain amount off of long standing existing depositing players then bam all the sudden you notice the same amount of players are in the casino BUT your earning way less then the norm, again that would have to go on for a few months before you can get suspicious. OR you have a whale that disappears over night into that deep blue beyond( all us longer timers have had this happen more then once)