I don't think it was a dutch warmblood. They don't come that small, (my boy is 16.2hh and he's considered quite small). Some warmbloods are nice to ride no matter what their age is however, keyword being some.
Don't restrict to just one breed! Every horse is an individual and the best horse can sometimes be the most unlikely breed (the calmest horse I ever rode was a throroughbred)