After what you said... if i ever build a sump, it's definitely inside!One advantage to having the pump inside the sump is if there's any leak in the hose connection to the pump, you don't end up with a flood. In fact you won't even realize it is leaking.
I had a set-up at one point with an external UV, a cheap made-in-China knock-off brand. My hose connections were all good, but after 2 years the UV unit itself developed a slow leak. Fortunately it didn't happen while I was away, and I caught it before I had a flood.