This is a benchmark battle between my old site and my new one. This isn't a completely fair comparison, as the Silverstipe site was hosted off of a shared GoDaddy server and the static site comes directly from an AWS S3 bucket backed by Cloudfront.

And the numbers reflect that clearly:

Homepage

E.g. http://www.posty.co.nz/web-development/

Old New % Difference
Load time (seconds) 6.12 2.21 -63.89%
Size (kbs) 1500 384 -74.40%
Number of requests 18 11 -38.89%
Pagespeed Score - Mobile 61 82 +34.43%
Pagespeed Score - Desktop 75 86 +14.67%
Blog Index

E.g. http://www.posty.co.nz/blog/

Old New % Difference
Load time (seconds) 2.87 0.78 -72.82%
Size (kbs) 1300 1100 -15.38%
Number of requests 25 20 -20.00%
Pagespeed Score - Mobile 40 71 +77.50%
Pagespeed Score - Desktop 47 65 +38.30%
Blog Post

E.g. http://www.posty.co.nz/development/2015/12/11/breaking-away-from-the-cms.html/

Old New % Difference
Load time (seconds) 5.3 1.22 -76.98%
Size (kbs) 1400 397 -71.64%
Number of requests 62 16 -74.19%
Pagespeed Score - Mobile 42 74 +76.19%
Pagespeed Score - Desktop 68 77 +13.24%
Portfolio page

E.g. http://www.posty.co.nz/web-development/

Old New % Difference
Load time (seconds) 4.98 0.67 -86.55%
Size (kbs) 3700 544 -85.30%
Number of requests 31 18 -41.94%
Pagespeed Score - Mobile 21 78 +271.43%
Pagespeed Score - Desktop 67 90 +34.33%

This last one, the portfolio page, shows the biggest differnce between the two. Techniques like lazy loading images and using Gulp to combine and minify assets have huge benefits.

These numbers reflect what I said when I wrote about dropping the CMS. There are huge, tangible performance increases to using a system like this.