The only real resemblance to the climb from SJPDP is that it's steeply uphill. I much preferred the climb to the Somport pass, however. It's almost all on real trail, which (to my mind, at least) makes it more enjoyable than the slog on pavement on the Frances. It's also spectacularly beautiful, with the high peaks of the Pyrenees looming over you -- snow-covered in May when we walked, though probably not so in September. There are no services or places to stop, however, until you get to the pass, where there is an albergue. (There may also be hotels open in Candanchu, the ski resort within a kilometer of the pass, but they weren't open in May).
There also won't be a crowd walking with you. In fact, we saw absolutely no one once we left Urdos. Thus, pay close attention to the trail markers, as you won't be able to simply follow fellow travelers. We also relied on navigational guidance from mapy.cz, a wonderful free app. with all the caminos already on it -- meaning you don't have to download additional tracks.
From Urdos to the pass it's 13 kilometers, so that's about 3 kilometers less than the climb to the pass between SJPDP and Roncesvalles, and it's about 1000 meters of climbing instead of around 1200 meters of climbing on the Frances. If you don't want to stay at the pass, it's a further 7 steeply downhill (and still gorgeous) kilometers to Canfranc Estacion, with lots of services, and an additional 4 kilometers to Canfranc Pueblo, which boasts one of the great albergues on all the caminos.
I've walked a whole bunch of caminos, and I can't say there have been many other days that rivaled this walk.
Enjoy!