Will you have a lot (or even a moderate amount of) baggage? Will you have somewhere to leave this, or would you be looking at taking it with you?

Ryanair has the most restrictive baggage policy of any airline anywhere. You pay for all checked baggage, and if you're checking more than 15 kg then you pay an arm and a leg (up to 15 kg it's a nominal charge - something like £7 or £10). Carry-on is the normal 10 kg, so if you're just going for a couple of days and you've got somewhere to leave your stuff then you'll be OK.

However, if there is a choice I would still not use Ryanair. Their service is pretty abysmal, if things go wrong you're completely on your own ("Sorry, flight cancelled - we can fit you in on a flight in four days' time". NOT joking!), and they have a real attitude problem. I try to avoid them except as a last resort.