The output of the files: nginx or ftp?

Nginx ispolzuet built into the kernel of Linux command SendFile — nothing faster, no.
To make the statics on a separate server is good, the servers excellent.

With nginx load should be less. First, HTTP, unlike FTP, does not use different connections for sending commands and data; uses only one connection per client. Second, plays the role of a server architecture. For example, vsftpd for each connection spawns an additional process. nginx doesn't do the processing of all connection cycles in a given number of processes. Saving of resources is obvious.

nginx because less steps between a client and a server to receive content

Yes, the load will decrease. You can even keep some files in RAM to minimize disk access. Still recommend to play around with the network kernel options using sysctl (in a lot of online guides on this subject).

supported nginx. For example, FTP uses 2 ports, and http — 1. This fact alone says a lot. In General, the FTP needs to die, IMHO.

nginx IMO

experience — nginx,
earlier in dolgintsevo the era of distributed static on FTP, now only nginx.