I honestly don't know how this would go. Hal has superior feats overall (With much lower lows obviously) but Loki is way more intelligent and Hal's weakness is his ring. And Loki unlike most heroes is very likely to go for something of that sort.
Hal could do a Krona Buster on Loki for example and end it, but Loki isn't going to get into a pissing contest with anyone that isn't Thor and is almost impossible to kill/injure depending on your take with his powers.
Because his strengths lie in plotting and scheming and maneuvering his opponents into the weakest possible position; like most magic characters he's at his most dangerous when he has time to cast more complex spells.
He does have the ability to fight non prep of course, i just dont think what he has is enough to take out a competent GL, especially not Hal Jordan.
Gender: Male Location: Planning to take over the WORLD!
magic has been a weakness of the ring in the past (i've shown multiple scans in the past). not sure if that has been addressed currently or not. the ring has also had mixed showings vs tp and loki is a high end telepath and telekinetic. not sure how this would go but no one is beating the sh!t out of the other in this thing that's for damn sure. higher highs to hal but it depends if anyone can prove the ring vs magic. if not, then the heavy edge goes to loki. /shrug