Buying a palmtop may actually be harder to figure out than using one. Sure, they’re all one color (black), but the marketplace is full of choices. Does it fit easily in my pocket? (Unless you’re Paul Bunyan, most won’t.) Is it compatible with Windows 95? Does it recognize handwriting? How big (or small) is the keyboard? Will I need to buy a separate modem to handle e-mail? Does the screen light up in the dark? Should I spend $300 or $1,000? A NEWSWEEK guide to the top of the palmtop crop: