I have a Percheron. I don't think they are harder to ride than a light horse, I think in a lot of cases (as I've found) they are a lot more willing. It can be hard to find the tack to fit, depending on what size of draft you have.

With them it's all about respect and trust. They are NOT gentle giants. Ground work is essential in establishing a good solid foundation with them. I did two years of ground work while I was waiting for my boy to be ready to ride. When he was 4 I couldn't find a halter or saddle to fit him so I broke him riding bareback and in his halter.

Each draft breed has their own characteristics. I think the Percherons can be a bit saucier than some of the others!

Farriers are one of the most difficult aspects of owning a draft. Many will not work on them. When you do find one, treat them like a God.

A great book about draft horse ownership and care is "Draft Horses, an Owner's Manual", by Dr. Beth Valentine. It is THE best book out there on drafts. Everything you could want to know and more. You can get it on Amazon.com

Whatever you do, get a vet check prior to purchase. Good luck on your search!