http://gfycat.com also does this.
Live example with both formats automatically offered
http://gfycat.com/HonorableAdolescentFowl
Gif Size: 13M
Gfy Size: 2M
Compression: 2.7 to 1 (Bandwidth saved: 17G)
Views: 2082
Original: Video
Reddit comments: /r/battlefield_4