1) With FULL cache chosen the effects are to have the shortest session times and the largest footprint on the local drive.
2) With NO cache chosen, the effects are to have the longest session times but the smallest possible footprint on the local drive; it basically retransfers the entire file.
3) With intellicache selected the effect is to have a middle ground result. Only files above 500kb are cached, and the files which are less than 500 KB are re-transferred again.
We recommend using intellicache first, and in most cases it will be the best choice. The upload and download speeds is contingent upon your ISP speed and latency. We have tried to create a setting that would be optimized in most settings and most connection types, hence intellicache is the best choice for optimized backups.