I have the 3/8 and 1/4 drive sets in metric. The 1/4 set is a pass thru type set. The 3/8 is a conventional ratchet and socket drive system. Not only are the sockets low profile but, the 3/8 square drive is also shorter. See the picture below comparing a standard F80 ratchet with the RAF80 low profile ratchet.
For most (say 97%) applications, you can get by using a gearwrench but, for those oddball situations, it's good to have it on hand.
few side notes:
1. the mountain set isn't sold out at tooltopia, it's a new set. tooltopia has added it to their website and will offere it when ISN have it ready for shipping. new tools are always listed that way.
2. someone was talking about torque converter bolts. My favorite tool for those (since they're usually tight) is the SK or ez red XXL ratcheting flexhead wrench. low profile and length for torque.
3. given the infrequent use of a low profile set and the expense of the snap on set, i would consider the gearwrench vortex pass through sets, the mountain set, or even the kobalt version. the gearwrench flexhead pass through ratchets offer more torque with additional length.