It doesn't matter which you play. After you play an interesting game, stop. Look at it in detail. Use an engine. Did you miss obvious moves? When did the position start to not favor you?
Usually trades are my weakness. I don't calculate a line out enough and assume it will be equal with a stronger position. I end up a piece down and with tempo I might do ok, but I just made the position harder on myself. This is something that seems to carryover from one level to the next.
Standard, for the reasons given in bb_gum234's post.
G/30 should be your fastest, though even that is "quick" chess, and isn't the best for learning. Games of 60 or 90 minutes are better (with analysis after), though they may be hard to play here. Online (correspondence) is certainly a good option.
Thanks everyone for the replies! Do you think playing online or Standard Chess will improve my blitz games quicker thank exclusively playing blitz? I don't really have much of a desire (yet) to play tournaments, so should I just stick with what I'm doing or try some standard games? Thanks again!
Online and/or standard (with proper post game analysis) will allow you to improve your chess. At your level (and mine) Blitz will ruin it.
I never worry about my blitz game. Of course, I don't play blitz.
You can play some blitz games as well. But main focus should be on longer games. Dan Heisman says something like play 90 % long games (like 45|45) and 10 % speed (like 15|0, 15|10 or 30|0) or blitz chess.
For finding games with slow time control you could join http://www.chess.com/groups/home/slow-chess-league
And the chess.com standard time controls 15|10 or 30|0 are also far superior to blitz chess. There you could find opponents easily.
Your main task with 700 blitz rating is to not blunder pieces without tactics or to simple tactics. First you need some time to check if everything is safe. When you are getting faster with that, you will also improve your blitz.
Speed Chess helps you to be more confident when you play slow chess....
It also teaches one to react rather than calculate -- to play "hope chess." I find that even too much 30/0 causes problems with my ability to calculate in tough positions.
It`s not bad to have good intuition. In speed chess you often have to play your best guess.In slow chess sometimes too, e. g. when you only have spent all time but the 30 second increment. Or even harder when you have a time control like 2 hrs for 40 moves and half an hour for all remaining moves and you are on move 50 and have 10 minutes for all moves till the end of the game. There will be no time to check and evaluate everything.
But that`s not first priority, as said before. If this is ones main problem, he will already be good enough to "allow" some speed chess.
So I've been playing a lot of 5 min blitz chess and I've been hovering around 700 give or take for about a month now. I would like to get better but wasn't sure if just playing blitz games will help in the long run, or if I should spend time on standard chess games (like correspondence chess, but online. Whatever that's called.). One thing is I notice (and you can look at my recent games) is that I play at night, and after like 5 blitz games, my game gets drastically worse. Maybe it's cuz I play after work and I do get super tired after a few night-games. Anyone else notice this? Thanks!