re: Poker & Cash Game Buy In Amounts
Wow, tough question actually.
Do you take a knife to a gun fight?
If you get into a monster pot with a monster hand, do you want plenty of ammunition?
If you play with only 100BB's ($200 at a 1/2 table for example), are you doing this because your bankroll is not adequate, or you are scared to lose money (playing with fear, never good)?
Myself, I have developed the patience and discipline NOT to allow myself to play that way, and have the resources (bankroll) to absorb any loss (mind you, not a sustained losing streak for months), so I sit with the maximum allowed and those with bigger stacks aren't so big anymore, and can quickly be (all of mine), as I have enough chips to impact them, plus my stack allows me to make bets (and have chips behind the cards), that can influence my opponent.
For example: You have 175 chips left, you raise with AKs and still there are 4 callers at 15 each. $63 in the pot. You hit your King and bet 50, and get two callers. You have bet 65 and have 110 to deter or allow players to continue.
If I have 275 of my 300 initial stack left, same situation, I have 210 left, and depending on the turn card and the texture of the flop, my reads on my opponents remaining, I have more options than you (IMHO).
*Yes, I certainly can lose more with only one pair, but that negative thinking will bite you in the (_!_) more than help you maintain a healthy bankroll.
You have to have options and not have an insufficient stack (just like late in a tournament when you become short stacked and can't shake those with chips to burn and you get multiple opponents - instead of a one on one match), your chances decrease.