a)HTML or RTS b) is email open tracking possible?

JamesF

Currently using RTS as attachement, but debating going to embedded HTML. Pros/Cons? Do I really need to consider Mobile/desktop or various browsers? Any other considerations. I feel our attached file PDF of the sitelink form isn't really a modern approach. 

Secondarily, has anyone successfully inserted/incorporated an open tracker into email? IE: Mailchimp, hubspot, mailtracker etc. 

Thanks,