If you have to develop and rely only on SEO/SEM you can have any gTLD in the world. My most profitable websites are on .biz domains.
If you want to pass the "radio test" and don't lose traffic you need to use the .com in USA and the ccTLD in Europe. In Europe .com is acceptable and in most cases .tv too
But at the end of the day this is a domainer forum and at least 95% of new gTLD are a waste of money. It's not being "pro" or "against", is about making money and with dot dentist you'll hardly will.
But many many members here seems "supporters" not "investors".
I've done most of my profit in domaining with .tv, if in 5 years the extension will no longer be profitable I'll have no issue in saying "goodbye .tv", because is not my football team, is just a way to make money, and everyone should try to make profit in the easiest way possible, and no, dot diamond is not a easy way.