Are Viburnum trees or shrubs? I see 2 different pictures?

[BrownThumb65]

I need a privacy hedge that is green leafy from the ground up. I was told that Viburnum is good. I have looked at all the different ones and I am stumped as to why some look like trees and some look like shrubs?

I don't want a shrub that grows into a tree??!!
Is this due to pruning?

I will be investing quite a bit of money and the one I like is the Viburnum Odoratissimum (sweet Viburnum) because the nursery man said it produces no berries and will grow about a foot a month if well pampered.

Does anyone have experience with these as privacy fences? I need a full hedge. Thanks.

[MagnoliaMan]

The answer to your question is "Yes." Some are trees, some are shrubs, some are tree-ish shrubs, some are shrub-ish trees! I have used Prague viburnum as a huge screen. They get up to 10' tall and wide. They are getting ready to bloom now here in zone 6A. Prague is a willow-leaf-like viburnum with dark green upper leaf surfaces with silvery undersides (interesting in the wind). Pale cream white blooms, a broadleaf evergreen here in 6A. Tough as nails, I have them planted in a row that vascilates between oak shade and full sun and they only vary in height a small amount. The only thing they have suffered from is too wet (51" of rain, abnormal here last year). There are MANY others to choose from.
The Juddi viburnum by my back door is in bloom and its delicious scent hits me each time I go outside.
Gotta love the Viburnum genus!
Magnoliaman