If I had to choose between commemorative and definitive stamps, then my choice would be definitive stamps. Take for example the 1977 South African Republic definitive stamp series displaying protea plants. I got hooked with these in late 1990’s.
A full set issued in May 27, 1977 contains 17 different designs and values each having perf. 12½. The topic of the stamps are many faces of protea plants; appropiately the name protea comes from Greek god Proteus, who could change his shape at will.
Later on (in late 1970’s and early 1980’s), many of the values (3,5,6,7,8,9,10,20,25,30,50 cents and 1 and 2R) have been reprinted in perf. 14¼:14 . In addition of different perforation, one of the key differences between original and reprints are printing methods. Whereas the originals were printed using rotogravure process, reprints are mostly done on litho presses.
In addition there are sometimes very notable differences in paper used, such as thin and thick paper, and glossy and matte surface coating. These differences are IMO very easy to pick up when feeling stamp gently with fingertips.
And finally, there are 4 coil stamps that are imperf on top and bottom. Every fifth coil stamp may have a control number printed on the back of the stamp.
IMHO this set has all the characteristics of an upcoming classic stamp issue, and it’s definitely fun to collect both on general and more detailed level.
You might also be interested of related posts about Stamps and postal history of South Africa (RSA) and States.