Welcome!
1) I would say it really depends on the game system and setting. Just comparing the numbers of wanted ads doesn't give an accurate picture because usually a game will require 1 GM and multiple players. Plus a player wanted ad can always just be for a replacement player where a GM wanted is for a whole game.
2) By all means, no doubts about that for not just the above listed reasons. I GM a game and I spend considerable amounts of time more on that than the three games I play in.
3) Really much of that depends on the game, PCs, and the GM. I run a 12 player game, though it's somewhat expected that the players will break down into three 4 man squads.
quote:
I've found that a party even as small as four sometimes makes me feel left out or not useful.
Most likely the GMs fault. Unless you have a character with a very focused and specialized skill set, the GM should always give a time for each character to be in the spotlight. Now if you make a fighter pilot in a game where there isn't any jet fuel, that's your fault. (I've seen that exact thing happen.)
4) Not a clue, I despise D&D and have only played D6 Star Wars. If a game requires a grid map, you can post the map in the game with updates and there are off site pages that host maps that players can move their pieces on.
5) I think slightly more. With a MUCH larger player base, it's easier to find better players and find replacements for the inevitable dropouts. My game I turned quite a few players away and have always found a replacement in a short amount of time.