All About Symbian's recent review of the Nokia E51 as the "mini E90" made me remember an important factor to consider when purchasing a smartphone or PDA: the good ol' size vs. functionality dilemma. The E51 for instance, will never match the functionality of its bigger brother.

Obviously, a small gadget allows a lot more mobility. People won't wonder what's bulging from your pocket, and the lines of your expensive clothes won't be ruined. You also look like less of a geek, while compact smartphones come with less moving parts, leading to better durability.

On the other hand, it's rare for a small or anorexic handheld to feature the complete package. The RAZR 2 for instance may pack a very deep feature set, yet compared to a heavyweight like the E90, it's nothing. Power users also enjoy the convenience of a QWERTY thumbboard, as it allows much faster text input. A big screen is also always a plus. Both will never fit in a compact gadget, unless we come up with some holographic display and input technology.

In the end, working your way through this dilemma still requires a decent awareness of what you're looking for in a smartphone or PDA, what you need it to do, and what your budget allows. No matter how featured-packed or compact a gadget is, higher-end models will always cost more.

So what do you want? What do you need? How much can you pay?