In my opinion, yes because you're at different points in life. When i was 18 i dated a man that was 34 & it was definitely different. I wanted to go out and have fun and he worked a lot and also wanted sex fairly quickly. Which of course doesn't apply to all but it seems like the older you get the more guys Expect sex. I also dated an 18yo when i was 21 & my goodness i had to leave because he was very childish. I felt like he was in HS still (which i dont blame him seen as he just graduated) but i was already a sophomore in college so it was definitely different. So i guess it depends on the maturity level but to find someone 10yrs younger at a mentality way beyond their years, thats tough.
It depends on the people involved. I usually go for guys around 24. I think it can be difficult if the older person is looking to settle down but if both people are on the same page then I don't find it odd.