Will not change suspension geometry
Ride will stay the same as it is now
you will need them in case you ever want to bag your truck
Other than throwing the toe out of whack from stock spindles (alignment) there isn't a "bad" reason not to buy spindles.
Will give the same ride as stock (with stock coils)
Hangs down and scrapes
Cannot be used with spindles (safely)
Cannot be used with drop coils (safely)
more expensive than spindles
anotherblacks10 is right, this summer I replaced the LCA's that I had in favor for a spindle and spring setup, my ride height is lower than before and I also have more clearance under the truck because the LCA's have a 2" drop pocket.
But a 2" spindle plus your 3" springs may be too much drop unless you don't mind scraping...