id go with the 5 if i was in the woods and only could pick one, i believe the overall size is the same.
the main differences are ( correct me if im wrong)
5 - Glass breaker/pummel, Sheath Kydex - Thicker
6 - finger notch @ bottom of blade, 1/4 longer cutting edge, Sheath injected plastic - Thinner
here's a youtube vid explaining the differences
http://www.youtube.com/watch?v=sW7n8r3vvl8
The overall size is different. They also have different grinds (Sabre vs full flat), bow drill pivot in the handle of the 5, and the 5 comes with a bit different sheathing unit....the clip that goes onto the sheath for mounting.
Check out the clip I'm talking about:
http://www.eseeknives.com/RC5-new-sheath2.jpg
Here are the spec's from their website:
ESEE-6
Overall length: 11.75"
Cutting Edge Length: 5.75"
Blade length (end of handle to tip of blade): 6.5"
Blade Width: 1.56"
Weight (knife only): 11.8 ounces
Drop point blade style, full flat grind
Available in plain or partially serrated edge
Maximum thickness: .188"
1095 Carbon Steel, 57 Rc.
Removable lined Micarta handle slabs
Rounded Pommel w/ lanyard hole
The ESEE-6 is shipped with a molded sheath and MOLLE Locks.
ESEE-5
O.A Length: 10.88"
Blade Length: 5.25"
Maximum thickness: .25"
Weight: 16 ounces (Knife Only)
Finish: Textured Black Powder Coat
Handles: Canvas Micarta w/ Bow Drill Divot
Blade Width: 1.56"
1095 Steel - 57 Rc.
Sabre Grind
Glass Breaker Pommel
Serial Number On Pommel
Standard Equipment: Kyxdex Sheath w/ Belt Clip
The ESEE-5 is shipped with a black Kydex sheath and a Clip Plate.
Take a look at their website and it's specs, take a look at some of the other threads here and determine what would fit your needs best. Good luck!