Two months left till summer exams. I need to self teach one module and I'm hoping for 90+ UMS. Which one should I choose D1 or M1? I don't care which one is more enjoyable or boring. I'm purely in it for the grade. I don't do Physics.
D1 is definitely more straightforward for almost everything; there's only one topic that is challenging. That said, it's not as 'pure'/'mathsy' as M1 or the main core modules, so you might find the exam more difficult to ace since it requires some verbal answers.
Whereas, if you pick M1, it is going to be more difficult, but you know where you stand when it comes to the exams. If you've got the time, M1 is the better investment. If you have covered some mechanics in physics, you might find it to be an easy crossover.
Given that it's self-taught and that you only have two months (don't you have at least 3 months?), D1 is probably simpler. See what you think of it when you get going - you might find it really tedious.
I wouldn't recommend you self teach D1. I imagine the concepts and the algorithms would be hard to understand and learn without a teacher or at least someone explaining it to you. D1 can get very frustrating at times, you are either good at Decision maths or you can't get your head around it, and you would be taking a risk of going into the latter category
Also, I found M1 challenging initially but I believe that is the fun of maths! You will get more out of M1 even if you don't do Physics. M1 lies closer to the area of Pure Maths than D1 does and I think it would be much easier to self teach as there are some good textbooks out there Good luck either way!
I haven't studied D1 so can't say anything about it.
I will always prefer mechanics over other modules because mechanics is more interesting. You would have done physics at o-level, right? If yes, than you can easily do M1 at A-level without doing physics. I took M1 with chemistry last year and scored 100/100 in M1.
I also self-studied M1. The M1 edexcel book is good enough to understand the concepts, and if you are struggling to understand than examsolutions.co.uk is a great website to study it.
I basically taught myself M1 last year because my M1 teacher was terrible. I find that M1 would be easier for you because it's closer to C1 C2 etc unlike D1 which is completely different. However D1 is easier to remember but just takes sometime when it comes to learning it, and if you teach yourself from the book it sometimes doesn't have the right answer