If it was free I'd check it in. If it wasn't free I'd take carry on luggage.
The size of the bags allowed in the cabin is surprisingly big. The one I've just bought is H55 x W35 x D20 cm which is within the size limit for RyanAir and a large chunk of other airlines, if not all of them. The thing I'd be more concerned about is the weight limit. On some carry on luggage I've seen as little as 7kg allowed. Which isn't very much considering your bag may weigh a few kg itself. Although I've never had my carry on luggage weighed...
One more thing, seems like a lot of people have got lucky with short wait times with luggage. I don't fly often but have waited for more than 30 mins on several occasions at Bangkok, Heathrow and LA. LA was nearer an hour's wait.