As retired farmers, experience tells us that this time of year most cattle have just been let out of their winter housing. Therefore they are really just enjoying their freedom after being cooped up for months. Most will just be nosy and back off when challenged but it most definately can be scary when they are on a run! The one's to watch out for are the new mum's who will defend their young - don't turn your back on her.
Personally I find horses much scarier. We were caching a few weeks ago and as we were approaching the field with horses in, some deer scampered through, scaring the horses. This meant that as we went through the gate the youngsters were very very flighty, and Mr G had hooves flying too close to his head. That was scary and I was even contemplating jumping the electric fence - on or not.
Cattle or horses....... cattle any day