Personally, I think if they are going to wear collars than we need to create our own distinctive look so that people know they are Orthodox Priests. Wearing a Roman collar makes you look like a Roman and Protestant collars make you look protestant so people will assume you to be heterodox. Besides why would anyone want to look like a "priest" from another faith community? I believe many Orthodox would not even believe that there is such a possibility as a priest outside of the OC. I think we need to stop conforming to society and start transforming it.
But the thing is, I don't think we can transform society at this point, there are only 1mil to 3mil of us in a country of over 307mil. We only make up .3%-1% of the total population. Most Orthodox Christians are focused in major cities where they are a significant minority. The vast majority of the country has never seen an Orthodox Christian (or at least known it).
I also think that it is helpful to be identified as a Priest. First of all, it helps Orthodox Priests avoid suspicion by the authorities. Second, if Orthodox Priests are working in hospice or visiting a hospital, it's probably helpful for them to be identified as being a Priest and not just a nutjob wearing a black cloak. It also helps identify our Priests as being Christians and not as someone from another religion.
A couple examples:
Our Priest has often been mistaken for a Muslim or a Jewish man because he has had his cloak on. Even with his pectoral cross, people seem to be oblivious to it.
I also know another Priest who works in hospice in a major metropolitan area of over 2 million people. I don't know if he wears a collar or not, but if he did, it would help identify him to the families as being a Christian Priest.
I think it is also helpful to identify Orthodox Priests, especially if the Priests have semi-long or long beards, and/or are wearing their hats. (whether its a Kamilavki or a Skufia)
I wished we were a greater minority, but unfortunately, here in America, we aren't. I don't think we should ever compromise our faith or anything like that to conform to a foreign culture, but minor things like collars aren't a big deal. (I actually think pews are a bigger deal than collars, but that is a different discussion that shouldn't be in this thread)