So what I'm wondering is what are the practical differences between these two knives? Now I know this is the Becker forum and I fully expect to hear the Becker love. But I don't want fan opinions, I want practical information. Don't just tell me the BK2 is better, tell me WHY it's better. Tell me WHY I should stick with the BK2 and not bother with the ESEE 5.
Neither one is going to be very good at either slicing or chopping - they're very much all arounders, jacks-of-all-trades but masters of none. And although ESEE's quality is generally better as far as F&F goes, I don't think you'll notice a large difference between performance in their steel. So that said, I'm simply going to talk about the design.
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Handles
The 5 has micarta scales, which are much better than the very slippery scales of the BK2. But because you can put micarta scales on your BK2 and still come in under the cost of a 5 (or simply use some hockey tape for far less), I view that as almost a wash. The BK2 is
much better balanced in the hand than the 5, and the scales are much more comfortable. The 5's glass breaking pommel sounds cool, but in reality it's just uncomfortable and gets in the way.
Sheath
Depends what you want to do with this. If you just want a simple, stock sheath to wear low on your belt, the BK2 is the way to go. If you're thinking about customizing your rig, the 5 is the way to go.
Coating
I'm always found ESEE's coating to be far superior, but I've heard that the recent updates to the Becker coating close the gap a bit.
Blade Design
Just like the handle, I found the BK2's blade to be better balanced. IIRC, the blade has a little more height, and the cutting edge comes a little closer to your pointer finger. But it's not a significant advantage.
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I think you'd be better served by the ESEE 6 than either of these knives, but between these, my vote would go for the BK2. It's a better value and just plain handles better IMO. The 5 is a very nice knife but not as practical and comfortable as I would like.