I need to be careful commenting about batteries, as a number of people will simple say "just buy one" or some such.
But yes, that is correct. The charge time will increase also. Also, generally, the internal resistance of a larger battery is lower, those a little more efficient. So it is possible that the larger batteries will be fractionally more efficient and last even longer. But those values are likely too small to matter.

If the 1550 isn't too large, that would be a better alternative then the large stock extended battery which is hard to get in many cases.

I got one of their batteries for a Toshiba E805. It was a little larger then stock, but a lot larger capacity. Very nice.