I had a 4yo on loan for a bit a couple of years ago, he had a bad start to life and was a little 'tapped' and we named him phycho bobby!
He was lovely really, and yes had fab jumping potential! I would buy one again!
He eventually got sold by his owner, no idea where he is now.
As a child I had a welsh d x tb and he was an amazing pony - jumped like a stag and was quite fiery to ride but a lovely character. Definitely a cross I would recommend.
I really don't think you can generalise, every horse is different. I had a Welsh D x TB on loan years ago who was ace. I now have something which I think is probably a Connemara X cob, looking at him. He's nothing to look at, 15hh with a big body, little legs, huge head, tiny stumpy neck, nothing athletic about him at all but he would jump the moon, he is incredible. He'll skip over BE100 fences when I've been XC schooling like they aren't there, and made out last event last season, HT over a BE90 course, feel like 2ft. Conversely, my last horse was a 17hh ISH, v athletic looking, should have been a cracking jumper but hated it.
mines a tb x cob (presumably welsh) she loves jumping and is fairly bold. temperment mind varies...lately shes found fifth gear and wants to do everything at speed, shes sweet to handle and willing to please but just gets a little opinionated at times and lukes to bog off with me!
I had a cob x TB on loan and there were days where was like a cob, and days where he was like a TB. He had a fab jump on him but it was tricky to keep a lid on his exuberance! I broke 4 ribs twice then sent him back..... I did almost buy him
My late mare was a cob x TB who was an ex intermediate eventer and had evented with Jeanette Brakewell for many years. I'll dig some pictures out of her, she was a star!