If the course is accredited by the IoP then it will have certain core content that they teach you. Where universities do differ is in the range and difficulty of optional modules, how in-depth they go into those aforementioned areas and just in general how they teach and assess you. Depending on entry requirements they might spend more time at the start going over preliminary knowledge.
So even if two courses both mention things like quantum physics, special relativity, thermodynamics, classical mechanics and electromagnetism, that doesn't mean you're doing that content to the same extent at both. Stuff that's 3rd year material in one place might be 2nd year in another. One uni might teach general relativity as an option to undergraduates, another might not.
Also workload does vary between universities and between courses at the same university, it doesn't matter that they cost the same.