Hi!
I study Natural Sciences at Lancaster University, namely Physics and Environmental Science. I am currently in the process of helping my younger sibling decide on which University is right for him (to study Marine Science), so I'll offer you the same advice that I've offered him.
Choosing the right course can be very difficult, especially if you have visited both places and like them both. If you haven't visited both campuses, I would 100% recommend doing this- sometimes the 'feel' of a place can really cement you decision.
For me personally, the amount of field opportunities that my degree offers is something that is really important to me. I also really value lab time, so if there's lab specific modules that you like the look of, that can be really helpful too! I just had a quick look at both course pages, and they both have a page of module choices throughout the three years of the degree- so maybe do a compare and contrast of the two.
Another thing to look out for is the type of skills the degree is equipping you with. Some buzz words to look out for are GIS (Geographic Information Systems), R Studio/ SPSS, and data analysis. Modules that cover these things will be really helpful for both your dissertation, and for careers beyond University.
It also may be worth thinking about what your current interests are. For me, I really enjoy glaciology and hydrology, and have a good choice of modules at Lancaster in these themes. If you are really interested in atmospheric processes (for example), and one offers significantly more options to do with that, they that can also help to guide you in the right direction.
The final thing to look for is what extra-curricular experiences there are available to you in both Universities. Have a look at the societies and sports pages (normally on the Student Union websites), to see if there are things there that interest you.
Additionally, if this applies, have a look into disability support services, normally there is somebody you can contact to chat to about support provisions/ inclusivity practices.
I hope that this helps provide some insight, and good luck with choosing!
~ Niamh
Natural Science Student Ambassador at Lancaster University