Size advice needed for Revolution Country Traveller touring bike I'm about to by my first touring bike. I've got a very tight budget so I will probably order a Revolution Country Traveller from Edinburgh bicycle cooperation as it looks like it will suit my needs.

Though I would like some tips for which frame size I should choose. I know it's really hard for anyone to say what I will like the best but I've got no possibility of trying out the bike before buying. I haven't got any bikeshop nearby with a very similar bike in stock neither. 

I'm 20 years old, between 177-178 cm tall and my leg length (to my crotch) is about 80 - 81 centimeters. I've go a Specialized MTB with 19" frame which I feel suits me well and I've got a Nishiki Criterium (2008 or 2009 year model) in size "medium" which has a seat tube length of about 50 centimeters or so. And I feel quite comfortable on that bike as well. 

If I use the formulas based on my leg length I get results ranging between 53 - 55 centimeters. The Country Traveller is available in either 52 or 55 centimeters.

So, just by looking at what I've written above, what would you guess would be the best for me? I'm by the way not a very experienced cyclist. Even though I have had my Criterium quite a while I haven't travelled very great distances on it so I'm still quite inexperienced in general. 

All tips and comments are most welcome!

I apologize to all americans for using imperial measurement units by the way. But hey, google is your friend! ;)
The other question to ask is the length of the top tube and how that compares with what you have.  I agree with Kibbee that it sounds like with an 80 cm inseam, you should be on the larger bike.  Still, it is easier to get a long stem on a smaller bike if it fits otherwise.