Hey there. I actually just answered a similar question a week ago. I'll drop my answer below:
The benefit of holding the CAD version is to keep it in your home currency and avoid currency conversion fees. You also get currency hedging with those CDRs, which means if the Canadian dollar strengthens, you will not see the foreign exchange losses you would owning USD.
On the flip side, you pay for that hedging to the tune of 0.6%~ a year. This will simply be represented by a difference in returns of the USD version and the CAD version. And on the other hand, if the CAD weakens against the USD, you won't realize the currency benefits that would bring.
I opt to own the USD version for most of my holdings, just because I have a long-term time horizon and hedging is less useful in that situation. You end up just paying fees for effectively nothing, as currency fluctuations tend to even out over the long term.
A lot of this comes down to personal choice really. Some people like to keep their capital in their home currency, which is perfectly reasonable.
Just know that if you buy the USD version, a rising Canadian dollar will hurt you while a falling one will benefit you. Take this into consideration and then decide whether you want that exposure, or if you want to simply buy the CAD version and be hedged from this.