Thank you to everyone for your very helpful responses!
With regards to size, it's looking as though 10" is best for me. Even though I lose a fair bit of light gathering power, I get the bonus of portability and a cheaper price, which means I can buy some eyepieces, an Argo Navis, or maybe put the money towards a telescope later on.
Just one more question, how well does the 10" and 12" hold collimation?