Are you talking blade length or overall length? Assuming you are talking blade length, I EDC a blade length of 2". I'm pretty big guy @ 6'4" and have big ole knarly meat hook hands and I'd agree with JJ_Colt45 that handle design can make it or break it in this size. My personal EDC is about 5.25" oal. As a cattle rancher as well as a knife maker I use my knife a lot. I've never found it wanting or wishing I had a bigger blade. I make and sell a lot of sub 3" blade knives with the vast majority under 2 5/8" mark. Very useful for what we do. The wife also carries one the same as mine just a different handle material. Her's is in blue jigged bone and mine is in elk. Horizontal crossdraw is how we carry and is the method of carry preferred by the vast majority of my customers. The wife getting ready to rope at a friend's branding:
Mine at the same branding:
This is a Buckaroo my most popular model by sales. It is 6.5" oal and has a 2 5/8" blade. I also make this knife in AEB-L and then its called a Cowboy.
A Cowboy in elk:
Couple years ago my son was working on a nearby ranch. They had a first time heifer that weighed 1150 lbs or so... Then they called the butcher to see how he wanted them to bring the heifer in. He wanted her decapitated, the quarters separated, and the back straps pulled. So they did all that with the manager's Buckaroo knife I'd made him. We got a big box of hamburger as it was more than they could all eat, the two of their family's. Some of the best hamburger, bar none I've ever had.
Little blades are not found wanting.