Between your choices I'd go with the 15" steel. 15" wheels and tires are the more common sizes i.e. cheaper. You'll pay more for 16" sizes. Also, steel wheels are cheaper than aluminum.

My $.002


Terry Johnson
Gettin' Off 4X4 Club
'89 XCab SR5 V6 - D60 Hybrid SAS, Ultimate Marlin Crawler, Detroit rear, ARB front
'97 TJ - Atlas 3.8 Twin Stick, ARB F&R, custom rollcage