"Is it worth paying the extra for a hotter girl?" - thats up to you and your wallet
"Are they generally just as dirty and serve you with a passion or is it more wam bam thank you mam kinda service." - nothings guaranteed. its hit or miss, really depends on the girl, doesnt matter if walkup or hotel gal.
"I sometimes feel that some of the hot girls don't try as hard to please." - ???
It really depends on the girl, each person is different. And also, it depends on the rapport you build with them. Read up on the reports. Each girl is different.