The curve case fits perfectly on the wrist, even for a smaller wrist.
About reliability, from my experience of owning both watches, RM watch is probably not as reliable as Rolex.
And since the production of RM watch is very limited, the mass production movement of Rolex watch is much more reliable IMO.
The accuracy of both the watch really depends. My RM loss about 10sec per day and my Rolex gain about 2 sec.
However, accuracy is not really my main concern.