Honestly, to me it doesn't particularly matter because a young guy can be wise and smart as well as for a guy that's in his early 20s' or later in his 20s'. I'm 23, and I like guys that are younger than me: 18-20, and for those 20 year olds: 20-25.
I mean, I wouldn't date someone who's 30, I feel like that's too old for me. Uhm, but it can be a problem when you like someone who is 16 vs. being 25.. well because big age gap difference and where you could get in trouble and whatnot. So, it's usually better to date someone around the age range to avoid something like that to happen. Of course, you can do anything that you want, you just have to be cautious and know what you're doing.
I could date someone my age or younger, but I prefer older women, at least as old as 36. Women in their 40s are great too but family and friends tell me not to go that far. Older women are more mature and more special.
I personally prefer older men, not like old old I just mean 1-4 years older than me. More mature, more experienced.. Facial hair lol. And for woman (I'm bi) it doesn't really matter within reason of course