I have both SFs and SLs also. Both are great lights. Whether the additional attributes a SF offers over a SL is worth is a matter of personal opinion, tastes, and what not. As for where SLs are made, to my knowledge, yes most are made in China. However, again, TMK, the TL-2, TL-3, and NF-2 are made in the USA still. Here's how I see the two brands in various catagories:
1. Light output - about the same, tho the SL TL-3 bulb seems more efficient than the equivalent SF lamps.
2. Beam profile - because SLs have adjustable focus, the beams tend to not look as nice. There are artifacts in the beam, but in actual use, you don't notice these. But the SF beams are quite nice.
3. Machining - SFs are machined nicer. You can see they're more consistent in their machining. Both thread smoothly, but the SFs feel a bit better.
4. Aesthetics - SF's designs tend to be more "tactical" looking which appeals to a lot of people. SLs look more utilitarian. My favorite designed SL is the TL-2 LED gen2...very nice. But there's a lot more SF designs I like than SLs.
5. Thoughtfulness of design - SF designed their lights with the intentions to be swappable and compatible within their series. SLs didn't have that thought in mind, so you can tell that their lights are designed more reactionary, to come up with something within the smaller confines of what they've already released. Also, SF's LAs, tho pricey, are a bit more robust in that they will not fall out of the socket.
6. Value - If you're thinking about performance with good machining, SL takes it. As mentioned above, the additional attributes SFs offer, as well as the bragging/brand recognition (whether people admit it or not, that is a part of the SF allure), must be self evaluated.
There are other options for well made, high quality, high performance lights tho. Also look into the following:
- Pelican - I personally like the M6 2390, M1 2310, M1 3310, and the new M3 (not sure of the model). Nicely designed and well made.
- Inova - Only LEDs available, no incans. Nicely made with good quality, but personally not enough output for me.
- Wolf-Eyes - well made and performing lights. Made in China, but quality does seem to be there and they don't inflate their performance numbers.
- Blackhawk - Gladius and Falcata lights, well made and thought out. Made in USA also I believe.
- Nextorch - well made and some good designs for certain areas (their reflectors are quite good). Made in China, but like W/Es, quality seems quite good. Their performance claims are pretty accurate also. But they're a bit hard to get in the US.