Borders are like the scaffolding on buildings, fine during construction, but should be removed when the work is done. Table and frame borders have a utilitarian look about them making the pages look 'homespun' and unprofessional. Apart from cluttering the look of the screen, they nibble away at that most precious commodity - screen real estate. If you switch-off scrollbars, you are effectively fixing the frame size and anything inside it that doesn't fit will be clipped. Just remember that text changes in size from one user's machine to another depending on their platform, browser and personal preferences.
Graphic images are always a predictable, absolute pixel size.
If you put only graphics in frames, there is little chance of accidental overflow. If you put text in a frame, you can, at least, restrict its width using a table - so you only get a vertical scrollbar. Frames offer several advantages to designers. The basic concept allows some frames to remain static whilst others change. You might, for instance, want a common top 'banner' frame and a side navigational frame on every page and only one 'content' frame which changes.