I was about to ask the same question. Did a local purchase of including the Smith OTW but was out of stock so I was offered the ESS instead but opted out to wait. I see lots of people using the ESS and are happy with them but someone showed me their Smith with the fan on full, couldn't hear a thing so I was sold on it.

Thanks to everyone for the advice and comments. I think I'm leaning towards the Smiths.
I will post a review once I purchase and game them.

I have a pair of Smith OTWs. I was in the same boat as you between Ess and Smith. I chose Smtih in the end. My main reasons were:
- I had read some QC issues regarding Ess and didn't want to risk getting into problems.
- Lower pricing point
- Silent fan

I see that youre in Oakville, if you dont mind the trip and are going Smiths, I recommend going to Tactical Operations near Kipling and Queensway. They gave me a great deal and great service to boot.

Make sure you try any pair of goggles first to see the fit, otherwise you could be left with something uncomfortable.