hi, depends on your field, I can only talk from my point of view,
1. Bsc is just a bachelor and Msci is an integrated master in which you get graduated from a bachelor and also a master. however is a bit more challenging.
2. the good side of this is that if you chose to go for the Msci it's better as if it's your first degree you'll get funded the 4 years as an undergraduate course however if you take the Bsc, you'll get funded as undergraduate and then when graduated you decide to apply for a master separately you'll have to apply for a postgraduate loan which at the end you'll end up repaying 2 loans instead of one
3. I have applied for an integrated master in the STEM sector based on physiotherapy in which the more qualifications and knowledge you get the better, how're I don't know how it works around the field in architecture, if the experience or knowledge?
my English is not the best so I hope you get to understand what I mean, personally I'd opt for a Msci as one year more can help you after looking for a job long-term, is more likely to scalate jobs easily when you get started because of your degrees and also how much experience your uni offers.