Pic at bottom...
I have worn nylon and leather sheaths, with buttons and without. Quality is more in fit and finish then nylon vs leather. I'm referring to mass produced sheaths in general.
Generally speaking, I want the sheath to (no particular order):
1. Secure my knife, without it flopping around inside (proper fit).
2. I don't want exposed metal inside the sheath to scratch up my knife (although on work knives it's less of an issue if it gets other things right).
3. Fit securely on my belt without falling off or significant movement when taking out the knife. Usually, this means that the belt hole should match the thickness of the belt I am using, which also means I might have to change sheaths if I wear a significantly different belt.
4. Not feel like a miniature lunch-box hanging off my side. This includes analyzing how many objects I go by which try to rip it off my belt, i.e. a bush, an arm on a chair, a seat-belt, a door jam, etc. This usually means it doesn't stick out too much from my side, but knife size will play a factor in this.
Although I like the "idea" of using a sheath with buttons, there are some drawbacks. First off, not all buttons are good quality. Some break/wear more than others. The biggest issue I have with buttons, or my favorite advantage with Velcro, is that depending on the design of the sheath, if I forget to close the sheath, or if the flap is inadvertently opened, many Velcro flaps will re-secure themselves just from flapping back down without you even knowing it. There have been a few times that I went to take my knife/MT out of my button sheath and found that I had either not buttoned it well or it was open because it brushed against something. Luckily, both buttons and Velcro can be replaced if they wear out.
Last there are the obvious benefits of nylon not being sensitive to water versus leather being more tear resistant.
I usually wear a 1 1/2" wide belt, but recently upgraded to one which is very thick (3/16" thick x 1 1/2" width). Before that I would commonly wear the Juice in it's LM Juice button-snap sheath. I have similar sized button-snap sheaths for my SAK Cadet and Alox Pioneer X. Since they don't fit well on my thicker belt, I've switched to the
small Rainbow of California nylon (plus Velcro) knife pouch (sold at REI) for my Juice S2, CS4, Crater, SAK Alox Cadet, SAK Alox Pioneer X, and SAK Fieldmaster. I've been very happy with it.
I also use the
large Rainbow of California pouch for my BM 710 , Para2, RAT 1, and barely my Stretch without pocket clips, and they fit well. Rainbow of California sheaths come in three sizes and allow for both vertical and horizontal carry. With the large pouch, the vertical carry loop is large, so if I planned on carrying it more often, I would sew it closed slightly to fit more snug on my belt.
I don't know if SOG still sells the same Nylon pouch for their Paratool that I bought 25 years ago, but I am very happy with that for my Paratool, Skeletool witout clip, BM Mini Bone collector, and CS Mini-Recon.
I like the fit/finish and security of my LM Charge in it's factory button-snap leather sheath. I preferred wearing it horizontally, but it will no longer fit on my thicker belt that way, so I have to wear it vertically.
I really like my SAK Swisstool button-snap plus nylon sheath. I don't remember if there is a different one for the Swisstool vs the Swisstool Spirit... and if there is a difference I don't know which one I have. I don't have the Swisstool, but I bought the sheath for my SAK OHT which fits perfectly, and like it so much I bought two more (one for my BM Mini-Onslaught and one for my BM 940-2; both fit really well). It also fits my SAK Rucksack, but I don't carry that anymore. I tried a couple other Victorniox sheaths in a Victorinox shop (Mall of America, MN) made of Pleather and Velcro and didn't like them.
Right now I'm EDC'ing a BM Presidio in an adjustable Gerber Customfit Sheath. I like it, but it sticks out a LOT... even more if I try to shove a second knife/MT into the outside pocket. It is constantly getting caught on my office chair when I sit down. However, it is secure, it fits my Presidio fine (not bad for Surefire-style flashlights either), and I might even try their Quad version in the future... although I might secure one of them to my work Messenger bag.
Just some combinations of sheaths to MT's/knives. I switch different knives into different sheaths depending on what I think I'll need/want that day. My sheath/knife combos are described in the above paragraphs. Note - all of the leather sheaths
plus the Victorinox nylon pouch below have button-snaps; the SOG, Gerber, and Rainbow of California sheaths use Velcro flaps:
