From my experience, road races are generally easier for a fit "beginner" racer to jump in and stay with the pack. It probably depends on your strengths, but I found crits much harder starting out. Besides the constant surges, there are just a lot more opportunities to make mistakes.

I also find the average pace in road races much slower. It's doesn't matter that much when sitting in, but I see many more breaks succeed in lower categories in road races compared to crits. This seems particularly true in lower categories where crits are really short and everything is chased.

Finally, I think an experienced racer can "fake fitness" and get some results in a crit more so than a road race. I know several guys (sprinter types) who can jump in a 45 minute crit when totally out of shape and end up on the podium if the race finishes with a pack sprint. Unless a road race is flat, they tend to require some fitness to finish with the lead group and contest the finish.

This is from the perspective of someone that mostly races Cat 4 and Masters Open. I'm sure dynamics are different in other groups.