Youre right, -losis is painless and the one that bleeds. Angiodysplasia is a less common cause of GI bleeding than diverticulosis in px over 60 years, but history is the best way to distinguish (low fiber diet, chronic constipation, etc = diverticulosis)
Internal hemorrhoids will still be uncomfortable, and the patient wont have blood in the stool, but on the tissue (in trousers).