Ask HN: Custom code for sales/marketing site or CMS?

Those of you building the front sales/marketing/brochure sites for your startups, what are you using to build these sites? We are in the process of designing our marketing site and since it is mostly content, there is some temptation to use a CMS. However, I wonder if this can be a disadvantage when trying to track things like conversion rates, heat maps, etc. We'll also need a blog and I have no issues rolling in something like Wordpress for that. But since it can easily be used as a CMS, there's temptation to do the rest of the content as Wordpress pages too. Simple custom code using something like Sinatra would be a cinch, but carries some overhead of running a Ruby interpreter compared to a simple PHP site. Any guidance would be greatly appreciated!