Which one should I get? They both look great!
Buy the light for the XM-L
Put the XM-L drop-in in your favorite solarforce or whatever host.
Pop an old XR-E in the 501b and gift it to a friend!
They're directly driven so current draw is arbitrary between 2A-3.xA.
The real question is if they're legit quality hosts and dropins. There are some real crappy ultrafire clones out there but the real ones are good. That's also arbitrary until someone tries and reports back. For example, once I got a really nice 502b along with the shittiest xp-g imaginable in it (both driver and emitter pcb fall right out). Ignored my emails so never got any compensation and it took too long to ship to go through paypal. Dubiously worth it for maybe $10 for anyone with a job. That's how it works I suppose.
It's also notable that "great deals" are relatively rare from most of these vendors. I've generally gotten my money's worth from MF but never anything I would consider a steal.
From those two - The 502B
because it's built better? Or just looks?
Thanks bud :) Now why didn't I think of that? lol!
after some unfortunate losses due to clickies breaking, i often find myself questioning a purchase with whether or not i can find a cheap replacement switch for the light. Is there a source for 502b switches?
EDIT: nvm found them on mf :P
That's crazy! Small light, but lots of modes and very bright! Can someone who knows talk about all those lumens? Accurate? Sheeesh, my first light bought was a Xeno EO3 for $30. I could have got this one and a charger and a battery, and had a lot more fun! Can this be a decent light for that price? The KD C8 is similar but around $25. Is the C8 that much better, quality wise? Have to wait and see if anyone gets one of these...
Don't be too disappointed saypat! That Xeno is a gorgeous light, and of very high quality. When you start looking at hosts like these it can be hit or miss. The KD C8 is not a P60 host like these are, so they are slightly different styles of light. Only time will tell if these are half decent lights. For the price, it looks like a real bargain though!
its this in reference to a dealing you had with Manafont ?
No, Kaidomain. Perhaps it's just coincidence, but most of the hosts and lights I've gotten from them and Lightake have been closer to the original than DX and t-mart. DX is notorious for swapping out to crap after the first good reviews, I suspect they do this on purpose. MF has been ok, but the recent Skyray 3xml incident shows they're not exactly immune to this.
These look like Ultrafire clones. I have the Ultrafire WF-502D body and it look the same as the pics, the threads are smooth and the writting on the tube is clear and of good quality.. The UltraFire WF-502B threads look rough and the writting is not as good. The original Ultrafire WF-502B at only $6.94 looks better. But it may be worth the price.
At MF, that dropin alone is $12.25. http://www.manafont.com/product_info.php/generic-cree-t6-5modes-himidlostrobesos-memory-led-dropin-module-42v-max-p-5651
For the 501b, that's like buying the dropin and getting the host for $1.65... I'm really tempted to get this just to try the 28mm aspheric mod with the XM-L. It worked well with my XR-E R2 501b, but the light is so much more useable in stock form.
Good eye... they are obviously different drivers and this light is SMO instead of OP. I was just looking at the voltage limit specs. I still think it looks like a good deal though! 
I've just got MF L2 klone which has same driver as drop-in on a first link. Well, at least driver looks the same from outside. I'll check the current tommorow.
It's the same driver, as Kaidomain sell it:
http://www.kaidomain.com/ProductDetails.aspx?ProductId=11372
The thing about the 501B is...it's just plain.
The 504 is such a nicer looking and feeling host, and it has a smooth SS bezel. The Skyray $8 host is also pretty nice.
I have a 501 and rarely use it just because it seems too cheaply made. However, I have had no reliability issues with it at all. Perhaps I should relegate it to glove box use. Now the 501A I like a lot better, as a mini-p60 host. I would probably like it even more if it has the SS bezel of the 504.
Strictly aesthetic, I know, but for $7 more why not get something you are more proud of...
I wonder if anyone has the ENTIRE Ultrafire collection of flashlights and knives. That would be quite a lot of stuff!
That looks like the same KD driver here so it should be pretty bright on a decent cell.
http://kaidomain.com/ProductDetails.aspx?ProductId=11372
Just bought two WF-502B's. Will let you know how they turn up if they arrive.