I haven't actually played one yet, so grain of salt.
Studied Combat gets you half your level as a bonus to hit and damage, which means compared to a PF Fighter, all that's lost is a fourth attack that the Fighter misses with anyway. But the Investigator gets Studied Strike as a finisher. Meaning the Investigator has the basic ability to do decent damage all day long. Inspiration (Once you have Combat Inspiration anyway), and Alchemy boost it from there. You won't want to spend more than 1 round setting up anyway, so your unlikely to use more than 3 Extracts for a fight (and likely only 1), easily giving you the staying power for even a long adventuring day.
Plus, you get to be an excellent skill monkey, or abuse Effortless Aid as recently discussed.