I personally like the character I get from bittering hops like Columbus, Apollo, Chinook, and Warrior. Magnum a cleaner choice, but I wouldn't say it is better. Even though it's low cohumulone, it's also less characterful overall. I want to have characterful IPAs, not bland/boring ones. I would advise not overlooking the importance of your early and middle addition hops. They are more important than you think.
Some tips on lowering the perceived harshness/astringency in your IPAs:
*Use pellet hops and bag them in the boil.
*Try to do more 90 min boils, adding your first hop addition at 60 min.
*If you must do 60 min boils, be sure you have a full-rolling boil before your first hop addition.
*Try not to boil your hops for more than 1 hour.
*Focus heavily on the hopstand and dryhop.
*Work on your pH and mineral content.
*Don't mill your grains too fine.
*Don't carry over too much trub to the primary.
*Don't sparge with water hotter than 168 F. Also, don't over sparge with too much water. Try to stop the run-off when it gets to 1.010. The mash pH is increasing during the sparge and beyond this SG, you run the chance of stripping too much astringency from the grain bed. If you are measuring the run-off pH, stop when the pH rises to about 5.8 to avoid astringency problems.