As far as production is concerned, Lagoheidor has produced upper level jumpers in Europe (and dressage horses, and 2 approved sons). There are videos of him with his owner doing GP and a new one (posted yesterday) of him jumping with Anne Kurzinsky (spelling?) which shows you a couple of interesting things (ie contempt for small jumps, rideability - it must have been 10? 12? years since he was jumping and he is asked to go in a 'hunter frame' for want of a better phrase, so you can see him adjusting and coping, and his temperament when asked to go out of the box).
I have no idea about conformation differences. I have only seen one photo of Landwerder and he looked very nice - I think he might have been slightly smaller than Lago from what I remember.
Although I have to ask, if you considering Landwerder, then why aren't you considering Landor S? The huge advantage Lagoheidor has is that he is available fresh and that he is a dual producer. There is absolutely no doubt of any sort that Landor S is one of the worlds great jumper producers (just been named again by GOV as top producer) and if I were breeding for jumpers and could use frozen then he would be my pick of the 4.