Hi there!
Townhouses are brilliant- You get a huge kitchen, dining and living space with sofas, and the general look of them is great. Also cheaper then superior ensuite. However one downside is you have to share a toilet and shower, so it's up to you whether you'd feel prepared to do this!
I'm talking from superior ensuite view here- as in Cartmel every room is just that. You have up to 8 people in a flat, you get your own en-suite and share just the kitchen. It is more expensive though, however I know for myself, paying the extra money was worth having my own toilet and shower!
Lonsdale is also completely superior en-suite. From a biased opinion, if you wanted superior en-suite, I'd say pick Cartmel
But of course, that's up to you. However both of the colleges are literally right next to each other, so you're not particularly saving any walking distance time for example, if you pick one over the other!
This pdf is quite useful for seeing what each college offers.
http://www.lancs.ac.uk/sbs/accommodation/factsheets/ugsummary.pdfHowever the prices aren't right- they are this years. Next years prices are more expensive for every college and every accommodation type, which is annoying. But hey ho.
Hope this was of some help