When you play online you don't have much control over the map you will play. You can veto some maps off but in the end, it doesn't really matter whether the map is really played a lot or not, just your personal preferences.
In tournament, a popular map choosing technique is that the first map is decided either randomly, or every 1v1 starts on the same map. In Starcraft 1 Lost Temple has been chosen like this a lot in the early days (later on, it has been judge a little imbalanced because blocking the ramp gave the terran players a slight advantage).
After the first map, either the winning (rarely) or the losing (much more often) player would decide which map is to be the next. I'd say that most of the time, a 4 players map for a 1v1 is prefered since it gives each player much more territory to expand. Sometimes, they will choose "Steppes of War" in a "I want to rush you" fashion since it is the map where the spawning spots are the closest of the whole map pool.
So, on Battle.net, the maps are random so personal preferences don't impact the game much. Some maps are better for some races or some strategies (large choke points = harder to block = easier to rush).
Well, like most computer hardware questions - it depends.
What resolution will you be running it at (if you are using an LCD, probably its native resolution). What settings do you want to be able to run it at? (i.e. do you care if you have to turn it down to low settings, or do you want it to look great).
I found some graphs of frames per second on various different graphics cards, and it doesn't seem to require much (which is what I expected) - every card they tested gave good results!
TechSpot did an even more comprehensive review of hardware for SCII. Gamespot summarised the article thus:
The good news is that basically any modern graphics card will be able to run the game very smoothly on Medium settings, so even if you're not someone with a water-cooled monster gaming rig, you'll be fine. This isn't the most graphically-intensive game in the world.
But if you're in the market for a new card, want top-notch performance in the game without spending a boatload of cash, it looks like the GeForce GTX 460 is the card for you. It was recently released and can be found for about $200.
I don't know much about the current generation of graphics cards, but the GTX 460 [is available on Scan] starting from £120, which is within your budget. If you want an expert opinion on current hardware I recommend picking up a copy of CustomPC (my sub failed to update when I moved house, otherwise I would check it for you - WH Smiths usually have it). I think AMD are currently favoured over NVidia, but it's probably pretty close as usual.
Lastly - SCII is more intensive on the CPU than GPU, so double check that your CPU is fast enough too.
Best Answer
Well lets see based on the screenshots below
4x3
16:10
16:9
As you can see, the wider the screen the more horizontal space you can view. Thus, a resolution with a 16:9 ration would give you the most in-game vision. Also notice, the vertical vision does not change on the screenshots.
source: Widescreen Gaming