Content?
Generally TV screens have a sharper image but are frequently smaller and more expensive than a projected image.
Films or similar media normally look better when viewed on a screen
Multiple screens?
You could use multiple TV screens to solve the size of the display issue, although potentially this move the focus of the audience away from the presenter/teacher.
The solution also depends on the level of interactivity required.
Ultra Short Throw (UST) projector
One reason to replace ceiling mounted projectors, is the glare for the teacher, when facing the class (especially for a low mounted projector).
Wall mounted Ultra Short Throw (UST) projectors that are fitted above the board, remove this glare and may be used with an interactive whiteboard.
Alternatively consider a UST projector that has interactive functionality as these may be used on a wall or dry wipe board, without a costly interactive board.
