Do I want a 4MS or 8MS response time on my monitor?

Answer:

It depends, you should be ok near the 8MS if your a general user. If your for instance a gamer, you would probably better sour with the 4MS.
Either one, depending on price. If you can achieve a 4MS one for a similar price or for just a touch more, go for it. 8MS isn't that unpromising though, its great for general use.
low-grade the response time better the monitor. but it depends what you are gonna use it for. if you will run graphic intense applications, approaching games, then 4MS will be a better choice. but it comes beside an increase in price.