[waarior]

Both monitors you are considering getting(Dell E207WFP, Samsung 204BW)have a resolution of 1680x1050.

With resizable tables at most sites now the resolution "needed" to multitable without overlap is lower than previously. That being said the higher the resolution the more tables you will be able to fit at a given size.
For comparison:
The dell 2007fp 20in has a 1600x1200 resolution.
Dell 2407WFP-HC 1920x1200.
The Dell 30 inch and other (Apple, Gateway etc.) are 2560x1600.

The higher the resolution the higher the price regardless of the size. Same reason that Full HD 1080p(1920x1080) televisions are much more expensive than 720p (1280x720) at comparable sizes.

You would be able to fit the same amount of information on a 50in HD Plasma as you would on the 24in dell computer monitor. But the larger size will make the image larger.

So the "best" monitor for multitabling does not have an easy answer, depends on your budget, tolerance for small size etc..