"Better" is a matter of requirements. You can interpret a stream of bytes of MIDI with some tens of lines of C code and a couple of bytes of interpreter state. The physical interface is less than a handful of components. For OSC you need an IP stack.
Except a lot of MIDI in control type situations (lighting, user triggers) is run over ethernet these days. So if all things are equal on that front, OSC is a far superior design.
It almost doesn't even matter because outside of musical gear, OSC is becoming the established standard to control everything from DMX lighting to VJ software to OF/Cinder interactive installs to some more performance oriented software like Ableton Live (via LiveOSC).
I've written software MIDI sequencers (all the way back in the early 90's even) and you'll never be able to convince me MIDI is better than OSC.
Sorry, a brief glance at the OSC website would have corrected that misconception.
That said, I only assumed as much because I don't know of any OSC client software that uses anything other than IP networks to facilitate device to device communication. I googled for serial OSC software and found some nonetheless. Does your software support OSC over serial?
I used to do a lot of experiential retailing experiences and OSC was our preferred control scheme.