Yeah, Letus35 Ex is the way to go. Cheapest, only .5 (i think ) light loss, very good warranty and customer service, little setup time. You can't go wrong.
Does anyone that has posted in this thread actually own the LetusEx Yet ? If not Downsouth keep that in mind when making your decision. They are going off of the same information thats already available to you.
Each adapter has it's pros and cons and you should weigh those to make your final decision.
Pros
The brevis has interchangable diffusers, it's lightweight and subjectively loses the least amount of light.
The Sgpro is very durable and it's image quality is probably one of the best out if not the best.
The LetusEX is a good balance. It's image quality is great, it's also lightweight and flips the image.
Cons
The Brevis image quality might not be as good as the SGPro
The Sgpro requires rails and is heavier plus there is a 3 month wait to get it
The LetusEx I can't talk about cons because it's not in the hands of the masses yet. Which is kinda a con in itself
*Disclaimer - My opinions are just that opinions and I don't make any claims as them being the final or only answer. Please do research and come to your own conclusions
I bought a Letus a few years ago (I think I spent $350!), but I love it. The older one has a gg element that does create a lot of vignetting, but I can get around that when I want to. Quen is really nice to work with and is obviously very talented. The only thing that I don't like about the Letus adapters is their lack of support rods.
For the type I have, the adapter threads onto the camera lens, but the weight seems too much. When I use the adapter with the DVX, I am constantly having to support it myself. I haven't yet seen anyone who has created a rod support attachment for the Letus.
Basically, the new Letus is $900-1200, the M2 is $950 (and that includes the rods), and the Brevis is about $1100 (with the acromat) and I think those are Canadian dollars. Hope this helps!