Yeah yeah, Scyther has its crappy typing and the HUMONGOUS stealth rock weakness... But in my opinion, I'd use Scyther more. In the world OU, there are a bunch of fire types, wrecking my Scizor every day. With Eviolite, Scyther is superior in defenses so which mean, it's quite better in most of the stats. It's bulk may me mediocore with at least solid defenses and horrible hp, but other than speed, defense and attack, both Scyther and Scizor are equals and not counting the Evolution difference. They would rather be totally different Pokémon like Pinsir and Heracross than be an evolution line.
However, in the world of UU, RU and NU, Rock Types are abundant but my Scyther survived a whooping Rock Slide from an Aggron. Scizor can also survive it's greatest weakness with Iron Defense, Substitude and other defensive support moves its movepool can offer. So, both Pokémon are equals in terms of stats and since Scizor has only one weakness which is a HUGE one while Scyther has over a trillion weaknesses, I'd say I recommend Scizor but I still like Scyther more. Hey! It's my opinion so don't take me too seriously!