Never had a Keffeler personally, so it was nice to see some feedback here. I've always heard great things about them.
I can certainly vouch for the awesome craftsmanship and durability of the MBB work. I have had three different MBB blades pass through my hands (M8 - 8" fixed blade, M5- 7.5", and a beefy Karambit) and I myself own 1 custom M-30 which is ~5.5" blade in ZWear. ZWear is totally insane steel.
The way they forge & heat treat it is amazing, built for toughness & true hard use. They're also totally custom, forged personally by the three brothers, and can take one hell of a beating if your daily use requires so. I would definitely not hesitate to recommend them or use them. Also great dealing with Alan if/when any questions or issues arise. Really good guys with A+ customer service.