The larger screen and the the increased resolution that comes with it is very useful if your usage pattern means you need multiple windows open side-by-side or stacked etc.

If you're only looking at one window at a time then maybe it's as handy but even then, having chat windows etc always visible while working on other things is also useful in my opinion.

Personally, if the money wasn't an issue then I'd always go for the larger screen.

It's not too big. The only important thing in terms of placement is that the bigger one is 5" wider. Unless you have a tiny desk that just will not fit the 27, it's the one to go for.

The base 21.5" has a weedy spec in a few areas so you look at the higher spec 21.5 - and then it's only £150 to jump to the bigger one.

A shame Apple moved away from their 24" 16x10 screen, which was perfect.

To me it depends how far you are sitting away from it. Moving your head too much because you're straining your eyes would make it too big imo. I've got a 21.5. Mate has a 27. Mine's adequate in our office.

Depends entirely on what you're going to use it for.

My personal preference is two 21s...

Do Apple offer a trial period?

Get the 27. I work from home writing reports and have two 24" monitors. The bigger desk top is essential IMO if you do a lot of word processing work, as most people will, in a business context, have two or more reports open at the same time and it's really really helpful to be able to have them open side by side.

I got a 24" monitor, dualled it with an existing 19", after much soul-searching and "is it really worth it" internal conversations.

I'm going to replace the 19 with another 24".

Get the 27" if you can afford it, you won't regret it.

I've got a 27 inch monitor on my PC and it makes the 22 inch monitors we have at work feel cramped. If you have a bigger screen it can double as another gismo for watching films and tv on.

27" all day long - a wonderful thing to work on.