Of the Grado phones I have actually owned:
PS-1 (with bowls)
HP-2 (with flats)
RS-1 (with bowls)
RS-2 (with bowls)
GS-1000 (with bagel pads, but with bowl pads they would fall somewhere in between the RS-1 and RS-2s).
HF-1 (with bowls)
SR-225 (with flats)
MS-2i (with flats)
SR-60, SR-80, SR-125 (all tied for last place)
Overall, the absolute sweet spot in the Grado lineup when a price/performance ratio was the primary factor, the honors would go to:
MS-2i
SR-60
My desert island Grado would be:
PS-1
My preferred amp for all of the above phones:
MAD Era+ Purist HD
Preferred music on all of the above Headphones:
Metal, Rock, Punk & Electric Blues
Grado Phones best assets:
Nothing can do overdriven/distorted guitars like a Grado phone can. Looks (some love the looks, others hate the way they look - I think the retro-look is sweet). Most of the Grado phones are easy to drive and sound good plugged into just about anything. They hold their value for re-sale very well, as a matter of fact, the more rare and discontinued models often sell for 2 or 3 times their original price! Pad swapping - many different pad types available to tweak the sound to your liking.
Grado phones weakest assets:
Small soundstage (only exception is the GS-1000 with bagel pads). Hit or miss quality control (sometimes the phones produced by Grado are a work of art, other times not so much). Not comfortable for long listening sessions (except for the GS-1000s). Not easily accessible, or affordable to people living outside of the CONUS. Somewhat fragile compared to other manufacturers phones. Cord twist (this is one of my sore spots for Grado phones, an exception would be the HP-2s - those rod locks are freakin' SWEET).