I can't really comment on Dahua but Hikvision have a pretty sizeable market share, consequently, local support is quite good.
Hikvision devices also come with a 3 year warranty, regardless of what spiel some installers spin you.
For a basic system like you've described, either brand would work fine, it's much of a muchness at that level.
Edit: 3 year warranty applies to all models except their plastic range, that's 1 year warranty.