It is going to depend upon the speaker type (as well as some other things). For example, with long ribbon speakers, typically the vertical dispersion is less than with most other types, so a tall ribbon might actually be better in that regard than a bookshelf speaker, though it depends upon what specific speakers we are talking about and how they are placed in the room, as well as the acoustic properties of the room. In other words, you have no more worries than with a smaller speaker, except that you are likely to have fewer choices in where to put a larger speaker.