Personally, I'd prefer sheet cake. I'm the least graceful person on the planet and I don't think I can eat a cupcake without making a mess. (Yeah, yeah, I could just use a fork, but that seems to defeat the purpose of a cupcake...)
I'd think sheet cake is cheaper. We're also doing a 3-tier cake, and then a sheet cake for the rest. They'll just mix them all together when serving and hopefully people don't realize. And if they do, well, eh.
I prefer cupcakes because you get more frosting. Frosting > cake
It looks great, you don't have to worry about large tiered cakes...but the downside was, I ordered 100 cupcakes, and for some reason, they only put out 50,..so guests did not take multiple flavors that were available to them because they thought there would not be enough. So if you do cupcakes, I would instruct your coordinator to have them all out, if possible.
we also ran into the fact that the "older" crowd waited to receive a cupcake/slice of cake instead of helping themselves
If it is cake and has icing, I don't have a preference on how it is displayed in front of me. I do like the look of some of the cupcake displays. I do think sheet cake will end up being cheaper though.
Cupcakes are the way to go. If you do get sheet cakes, don't forget to ask your venue if there is a cake cutting fee associated. ( Some charge because they have to serve it with their cutlery, extra dishes etc)
I suggest cupcakes for a lower budget. A lot of place charge a cutting fee. I paid $300 for sheet cake and $350 for the cake cutting fee. I am currently making a cupcake stand, cupcakes and a small cutting cake for a wedding this weekend. People love cupcakes, they are portable and require to plate/knife, fork etc. More people will eat them from my experience.
If you're not dealing with a cutting fee, I'd say go for the sheet cake. Or better yet, get several plain cakes and put them on either a multilevel cake stand or a series of cake stands in different heights, with the taller ones smaller than the shorter ones. (See pictures, below.) You can decorate them with some plain organic flowers if you like. But using plain cakes instead of a fancy tiered wedding cake will save you about the same amount of money as a sheet cake, and will look more festive.