Yes, they bypass is more prone, or predisposed to, ulcers than the sleeve (just as the sleeve is predisposed to GERD.,) but they are a different sort of ulcer than what you have. The bypass tends toward marginal ulcers around the anastomosis (junction) between the new stomach pouch and intestines. This is because the part of intestine that is now immediately downstream of the stomach is not resistant to stomach acid like the duodenum - the upper part of the intestine immediately downstream of the normal stomach, which gets bypassed along with the remnant stomach in the RNY. Consequently, that anastomosis is very sensitive and prone to ulcers, which is the root of the "no NSAID" rule that permeates bariatrics - you don't want to take any medication that could irritate that anastomosis (there are other meds that may be limited, too, but NSAIDs are the most common class.)
What I would be concerned about is what caused your ulcer, and whether that cause would be relieved (or exacerbated) by your surgery. Similar to your hiatal hernia and GERD - fixing the hernia will likely correct your GERD and you will be back to "normal" - no more predisposed to it if you get a sleeve, but still possible. One of the problems with the bypass is that it leaves you with a blind remnant stomach and upper intestine, which can't be easily monitored with an endoscopy, so if something develops in that blind section, you may not know about it until things have progressed more than you would like them to progress (possibly to a cancer.)
Some express a dislike for the sleeve because if they have a resultant reflux problem then it could lead to Barret's esophagus and possibly cancer, which is a fair concern; however, that is something that can be easily monitored endoscopically if those symptoms develop, and can be treated; problems that may develop in the blind stomach or intestines of the RNY may not be caught until it is too late to treat effectively, so there is a trade off there.
You are somewhat caught in the middle, with some contraindications for both of the common WLS procedures. This is where some serious talk, and understandings, with your medical team is appropriate to really get a good handle on your problems going into this, and how those may play out in the future. I/m not so sure that I would be comforted by the matter that the surgeon may be able to work around a problem (such as an ulcer) if that problem is likely to reoccur 5-10 years in the future, and possibly worse - the surgeon is out of the picture by then, but you aren't.
There is another alternative that might be worth considering, which would be the duodenal switch - it uses a sleeve, so it doesn't leave a blind remnant stomach, but due to its' malabsorption component, they typically use a larger version of the sleeve which is less prone to GERD problem. Your surgeon may not offer it (it's a more complex procedure, so many surgeons don't offer it) but it may be worth looking into to see if that fits your need.
Good luck,