I find IOE to be even less certain than reserve. On reserve you have days on and days off, and you can see what trips are open, you know how many days you are good for, etc. On IOE you are constantly just waiting for the phone to ring. Might be a day trip, might be a 6 day trip (including travel). Your callout times are better on IOE. I’ll give you that.
Depending on how you look at it, it could be slightly better than reserve, but it’s no where NEAR the certainty of a line.