Totaly worth it.
I had a dratini 97% with 10 CP and a dragonair 100% with 800CP, evolved both.
You will only have a prejudice in candys, but my dratini with 10 cp cost just ~50k stardust and ~60 candys to put him with 2300 cp (plus the 125 to evolve him to dragonite) but totaly worth it.
So invest in the 100% iv one