Hi
@legallady123 I think that if there is any disadvantage, it will be only a very slight one. In many cases, for myself included, a sufficiently high-quality application was progressed although it was only sent in the last day of the rolling period. Moreover, rolling firms also receive the vast majority of applications in the last 3-4 days before the deadline. Thus, your application should still stand out from the crowd in the right way in regards to the submission time.
However, if you are just concerned with absolutely maximizing success chances, you could also consider just submitting the application for the summer scheme - that way, you would be sure to count as an 'early bird'. However, this success chances calculus is further complicated by the claim that, all other things being equal, winter/spring schemes can be slightly less competitive than summer schemes because (i) some international students cannot apply for them; (ii) some students who can apply might choose to prioritize summer schemes instead because those will not take away form the exam revision time; and (iii) that the summer schemes application deadlines are later in the cycle and thus allow for more applications from people who procrastinated or just started their applications later.
My personal opinion is that there is no sensible or even potentially accurate way of trying to calculate such abstract odds. If I were in your place, I would simply apply for the period that is more convenient for me.