Hey Paul,
Really ... thats all going to depend on how early or late a Blackhawk you want. Me .... I like Academy's 1/35 AH-60L DAP Blackhawk. I know you said 1/48 or 1/72, but this is a great kit, and at a decent price. Plus, crew and figures are easier to find in 35 than in 48, but thats just me.
Also ... check out http://www.aircraftresourcecenter.com , its got pretty good reviews for lots of kits. You might find one that more suits you.
Hope that helps.