There are two types of DDoS attacks, which Github actually wrote about last week (thereabouts[1]), although you'll be unable to read the blog post until the site is back (unfortunately).
But I can outline the two they discussed. The first is a "complex attack", which basically consists of doing things that make the server overload itself (repeatedly handshaking SSL, etc.), and that would be mitigated to some extent by reducing the complexity of the site (i.e. you can't SSL handshake with a server that only knows HTTP). Similarly, dynamic content could be an attack surface, so static content would make it more difficult to use such a complexity attack.
The other type of attack, a simple bandwidth attack, doesn't care if your server is a top-of-the-line quad-chip Xeon server or an RPi in your basement, because all it does is exploit the bottleneck that is bandwidth. This attack just pumps packets like mad in your direction, and your network will likely become congested (and eventually fail) at some level other than your server (i.e. router level, firewall can't handle 100 Gb/s so the packets never even make it to your server).
So, in light of the second there, DDoS'ing static content is just as easy as DDoS'ing dynamic content sites, as long as you're using a bandwidth type attack.
I encourage you to read the blog post when the site is back up, it's definitely worth a read!
But I can outline the two they discussed. The first is a "complex attack", which basically consists of doing things that make the server overload itself (repeatedly handshaking SSL, etc.), and that would be mitigated to some extent by reducing the complexity of the site (i.e. you can't SSL handshake with a server that only knows HTTP). Similarly, dynamic content could be an attack surface, so static content would make it more difficult to use such a complexity attack.
The other type of attack, a simple bandwidth attack, doesn't care if your server is a top-of-the-line quad-chip Xeon server or an RPi in your basement, because all it does is exploit the bottleneck that is bandwidth. This attack just pumps packets like mad in your direction, and your network will likely become congested (and eventually fail) at some level other than your server (i.e. router level, firewall can't handle 100 Gb/s so the packets never even make it to your server).
So, in light of the second there, DDoS'ing static content is just as easy as DDoS'ing dynamic content sites, as long as you're using a bandwidth type attack.
I encourage you to read the blog post when the site is back up, it's definitely worth a read!
[1] https://github.com/blog/1796-denial-of-service-attacks