If you plan to keep the car fairly stock, there is no reason either would not be reliable as a daily.
I'm personally not the biggest rotary fan, so my choice would be the R33.
But as marc280 said, it has abit to do with the driving style of each too. I do prefer the low down power a piston engine gives.
I do enjoy driving the RX-7 (friend of mine has a series 6), but I love my skylines more.
When it comes down to choosing a daily driver, you have to look at it from a few angles. Obviously it has to be comfortable to drive no matter what the traffic conditions. Also fuel consumption can play a factor.... You are driving it everyday, and the costs can add up.
The bottom line is you need to be happy stepping into it day in, day out.
Cheers,
Alex