So, which do you think is better for medicine, and why?
Things I'd like to consider when deciding between the two include the areas where the campuses are situated [since I'm gonna have to be there for 5 years], the intellectual stimulation of the courses, social life opportunities etc.
KCL's Guy's Campus looks great and is near London Bridge, which is a very aesthetically pleasing area. It also has a higher general reputation than Barts, which counts for next to nothing if you're doing Medicine.
Barts also looks great, but is based in Whitechapel (which has its pros and cons). The area leaves much to be desired, but is a lot cheaper than central London and is easier to commute to for most people. They also (supposedly) have access to a wider degree of conditions, due to the demographics of the area.
I can't speak for the social life (though I'm sure they'd be great at either), but as for intellectual stimulation...you'll be studying Medicine. I'm really not sure what else you could want.
Just go to open days at both and decide then. You can't really go wrong tbh.