Why is it preferable to have higher-level people as friends?

It really doesn't matter. If you are trying to get friendship points, I have found it is better to have lower level friends since they are also trying to get friendship points and will visit more. People that have been playing a long time usually don't visit much because there isn't much incentive for them.

It...depends.

I'll put it this way, hwho would you rather hire, someone who has worked in over 20 different places this last month or someone who has worked in the same place for 2 years?

Ya dig?

As this is a game (and i do enjoy games) we often play at our leisure, some play hardcore others softcore, others however simply wet their toes and leave (something that was alluded to by Evil Homer, his universe didnt even have a Moe's).

So during events, you notice these things.
Yeah as a higher leveled player i've practically stopped visiting players towns (outside of events), but during an event? Something is always tappable, i will often move my landing area to better accommodate neighbors and i try to often visit as many as i can.
During more "co-operative events" like the Naughty or Nice for Xmas or the Gold prospectors, or formless terrors of THoH, i become a lot more active.

Lower leveled towns (below 20) who stay at that same level for too long will often mean they are inactive or do not frequent the game, when i come across their towns sometimes all buildings are tapped, or dropping something there will mean it will be received late or not at all (thankfully both prospectors and formless terrors would expire after a while so theres that)

one reason: Higher level peeps are more likely to have more content, be it old limited time stuff or new stuff that requires many donuts. And it's always fun to check out the new content or see old stuff or see what the person did with those items, etc.

Plus higher level folks have more tappable buildings during events.

I don't have a preference. I accept new players to help them along but also like veteran players because I like to explore their towns. I will accept anyone as long as they play on a regular basis.

It doesn't matter to me. I'm happy to help out new people.

I kept a mix of both. Low level players are good in events like the time travel ones as loading time are faster. High level active players generally are good in events with mutual benefits. As they are more likely to visit. I generally keep active players, be it low or high levels that bother to visit in events with mutual benefits.

During non events, I will selectively visit and admire the design of towns as I do not need the cash from visiting.

Pretty much what they said.
Really low level players can be a negative during an event, they haven't the buildings or characters to keep up. But I grab a few, just to help them along.

During events where you have to tap wandering characters, lower level towns are better. I prefer them to higher level towns.

I actually prefer newer people. I like watching their towns grow and develop. I have one who i watched from level 13 all the way to 939!