It depends on what you want to achieve.
It depends on what your budget will tolerate.
It depends on to which TerraLux you want to compare this one …
I’m pretty sure you don’t need to be told that your bulb is listed cheaper than the TL ones…
My first question would be, why bother? This is a “no-name” replacement bulb that will probably be dimmer, almost as hot, and won’t extend your battery life (at an unregulated downward curve the whole way) enough to make up the difference in cost over the probable lifespan of the flashlight. How well does this “SUT” company support their products, if you ever need such? Can you E-mail their support or engineering staff to get confirmation of the lumen output, or a definitive answer as to current draw, operating temperature, specific LED color bin, etc? Inquiring minds wanna know!
“thefusionlite” is just a Yahoo E-business re-ordering site — not to imply they wouldn’t replace a bad one, however unlikely that may be — but they may not even have one in stock they could test & report for you. Would you like to be the first to review one so we can all have some hard data to use for comparing? Without (preferably independent) review, anything any of us could give you is just SWAG from off the tops of our heads.
If you’re already committed to some TerraLux PR-based bulb, you could let us know to which we’d be comparing…
As for me, I have enjoyed upgrading $18.00 Mags with the $15.00 Sears PR-base LED and $9.00 CR123 battery sets, but you couldn’t give me one today, since I still have a new one I never found a host for, and the ones I have deployed almost never get used (too big, ooky Mag beams, ridiculous battery cost, etc.), meaning they’ll likely outlive me & get tossed in the trash. That’s what your $42.00 would get you in 1998. Oh, and there are entire flashlights you can buy on eBay for less than what just the OP bulb set costs, which will blow it into the middle of next week, in terms of output, lifecycle cost, run cost (unless you buy single CR123 batteries retail), and carry-ability.
As a first-order approximation, my answer would be “Probably not that different, probably not worth the risk unless you actually need one & can’t commit to 21st-Century technology just yet. Why don’t you order a set, smoke-test one under controlled conditions & publish a review here?”
Thanks for asking!
Dim