I made my own spray booth some time ago very cheaply and still use it but decided to see how good these little cheap ones really are so once again I hope someone might benefit from my findings.
The cheaper one ($42AU delivered, the winning bid $12) was the BD-512, it's the simpler of the two to setup but also the biggest on the outside but not the inside, here are a few photos that compare the sizes quite well.
As you can see the older BD-512 is a fair bit bigger than it's updated model but the newer 420 is two cm bigger when opened up, I have no idea what brand these are but I'm pretty sure they came out of the same factory but I could be wrong. One thing I didn't know about the BD-512 is that it has LED lights but there at the back and only in the middle so not the most useful. Also the 512 has a two position center off switch so you can just have the motor on or motor and lights on, for some reason thats not the case with the 420 which is either lights and motor on or off BUT thats easy fixed which I have done. The front openings are very different as well, the 512 front is more squared off than the 420 so you need to be in a more down looking into positionit where as the 420's top is well back so it's more comfortable to lean and look more down into if you can get what I mean, I found my forehead having issues with the top edge of the 512, others may not have that problem, here's a photo, as you can see the 420 on the left has more room for big heads.
Switch position is better on the 420, as you can see in the photo's at the top it's next to the DC input socket on the top right where as on the 512 it's inside the back of the unit and you have to reach into the back of the unit to operate it but it's no big deal really and far enough away from the cord retract button on the left.
The 512 is a 240 volt unit (Australia) and the motor is the RAH1238B1, it's power lead retracts into the unit for storage.
The 420 is a 12 volt DC unit and has a plug pack for operation which will store away in it's little hole once you figure out how to get it in but it can be done. The motor is a RDH1238B1 which is a higher rated motor and it sucks about one quarter to a third more than the 512 but as you would expect it's a bit more noisy too, there both rated at 47db but thats not correct, the 420 is noticeably louder than the 512.
The ducting is very different on both units as well, the 512 has a fixed lip and you use a 5 inch hose clamp to keep the 5 inch pipe on, simple and works fine and the hose comes in two parts but it's fairly limited flexibility wise. The 420 still has the 5 inch (120mm) fan and outlet but the ducting outlet can be off or on and it reduces it to 4 inches which is a lot easier to find alternative ducting if needed. Here are the two hoses compared and below that the 512 outlet with it's clamp, the middle hose belongs to the 420.
this is the 420 outlet attached to the unit with four screws. My modified switch can be seen better in this photo also.
To give you an idea of the flexibility of the two systems, I had to use my feet to hold the black pipe in place or it will spring back to straight. The 420 also comes with a flat window attachment which I will find handy when the air conditioner is on.
These two photo's give you an idea on alternative ducting, I bought this 4 inch plastic piping from England some time ago for around $20 delivered and I think it's dryer ducting but it slips right over the outlet and stays without a problem, you do get a huge hose clamp with the 420 but as yet I have not needed it.
Now for lighting, there's no comparison, the 3 LED strips that sit on the front top edge and down both sides are FAR better than that of the 512 lighting. It lights the work area very well indeed. I have four photos but it's hard to show exactly the difference between lights on and off, lights on are the right two photo's and unlit natural light on the left, the LED's seem a bit bluish in the photo's of the 420 on the top but the light is a crisp white.
here is the 512 LED's, as you can see all the light is from the back and leaves the front of the job in shadow.
A few notes. Quality of the two units is pretty good for the price, the 512's hinges are so so where as the 420 hinges are pins and more solid but both will last for ages. The door on the 512 will fall open very easy and I use a bit of tape to hold it closed, the 420 door latches underneath the front and is secure but when you open it the floor of the 420 can fall out.
Both turntables are good and can be used outside of the booth as well. The 512 turntable has three suction cups on the bottom and are close tothe middle so unless there stuck down well you can easerly push down on the side and tilt it which would not be a good thing most of the time, the suction cups stick ok on the plastic bottom well so all should be well. The 420 turntable has six normal rubber feet around the outside and is a lot more stable with a lower profile and not reliant on suction cups. Here's the photo's, 512 is on the left.
The worst thing to look out for with them is thinners, for some reason only known to the manufacturers the plastic is NOT solvent proof so don't wipe them with thinners or spill any as it will eat the plastic, I use a piece of thick card on the floor and that solves the problem with the exception of the suction cups on the turntable, might have to cut a hole.
As for the actual vacuum performance there both pretty good but the better CFM of the 420's motor naturally is better and is noticeable when it comes to fumes extraction. The 420 is the best out of the two and when used as designed with a airbrush I noticed no smell where there was a bit with the 512. You could not use spray cans id say.
I have read once or twice that the motors have failed after a short time, both motors have been fine for me so far and the motors are a very common type so I don't think there would be much concern there. If I have any problems in the future ill update this page
I bought a two position center off switch (ebay $5 delivered) for my 420 and fitted it so I could have the lights on without the fan, the insides of the 420 is easy to get to but if you do this mod be very careful with the screws as you can strip the thread.
For the price you can get the 512's for you cant go wrong but you would be much better off to pay the extra and get a 420, I got mine for $93 delivered with buy it now here in Australia but you can get them a bit cheaper. There great for me as I get close to my work when doing camo jobs or the not huge jobs but when base coating or spraying larger areas I use my home made booth as it will suck the budgie out of its cage.
I must give a big thank you to Don Wheeler who has checked out every review I have ever done before I publish them and offered his suggestions and help so Thank You Don it's very much appreciated.