I currently own an FD RX7 after having owned only nissan's for past 9 years (s13,s15,gtst& gtr's).
my answer is it depends on what you want it for.... IMO you can use the rx-7 as a daily if your not driving very long dist & if your not over 6''1-6''2 (without having seat rails modified).
they are better on petrol than a GTR if you drive both cars easily although not as good as the s15..... performance between an s15 & rx7 is worlds apart...rx7 is better in everyway possible...rx7 is more comparable to a gtr.
I use my car 2-3 times a week & have a shitbox for the other days...I could use the rx7 everyday although like a gtr it feels wasted plonking around in traffic.... thus far I have had no issues with reliability.
the main catch is that a good rx7 (00-02) rs model will set you back a good 30g or so...s15 prob closer to 20g.
send me a pm if you have any other questions