Marlin springs would not be my choice for any daily driven rig, they are too soft in my opinion.  My 4Runner on Alcans had less body roll without rear shocks installed than gotrocks 4Runner did with Marlin springs and shocks.

If you're considering Downey then there's no reason to not consider Superlift or Skyjacker.  I ran a Superlift 4.5 on my 85 and I don't believe my springs ever kept me from going anywhere.  The front springs worked extremely well, but the rear could be improved on easily. 

Downey and Marlin are not really comparable products in my opinion.  Downy are much closer to stock design while the Marlin springs were intended primarily for off road use.

I run Alcan, but not everyone is willing to fork out the coin.