I couldn't find the ACER or the Samsung monitor you posted (I found a S24B300EL...). I would go with whatever monitor has good reviews in your budget. I own the ASUS VE228H and it is a very good panel even more so for the price.
They are all pretty much the same except for the size. The enhanced contrast ratio manufacturers post are never true so don't bother with those numbers. If you want accurate numbers on achievable contrast then head over to www.tftcentral.co.uk for excellent reviews.
I would say between those monitors, it is all a matter of preference for brand. I personally have had a very good experience with ASUS and will probably stick with them for future monitor purchases in the low end segment.
I also forgot to mention the VS229H. It's an IPS panel if that sort of stuff interests you.