Will I notice any difference between displays of different sizes but same resolution?

"From Monitors - Resolution :

Compare a 15-inch monitor
and a 21-inch monitor, both set to 800
x 600 pixels: the 15-inch will have a
higher resolution. Larger monitors
must contain smaller pixels in order
to maintain the same resolution, but
when a smaller monitor is set to a
high resolution, the images would be
much too small to read. A 14-inch
monitor set to 640 x 480 is very
readable, while a 21-inch needs at
least 1024 x 768.

Meaning that a too small resolution on a big screen is as bad as too large resolution on a small screen.

The info in the above article might help you decide, but I believe it claims that on a 14-inch with 1366x768 resolution, the text might be quite tiny."