From what I've read/been told, there should truly be no difference. As in chances of getting a TC out of them are largely the same no matter which one you do.
It is possible that at some firms, winter and spring vacation schemes may be ever so slightly less competitive, purely due to people having less availability in these times. However, I think the majority of firms adjust place numbers accordingly, it's not really a massive difference. Also, perhaps the calibre of applicants is somewhat greater at winter/spring, since many will be career changers/graduates/finalists, and might have a bit more experience under their belts.
Sometimes winter and spring are shorter schemes though, only 1 or 2 weeks, where many summer schemes are 3. If you think you'd find 3 weeks too long then that's something to consider. On the one hand you've got less chances to impress, and learn about the firm and the job, on the other hand you've got less chances to mess up, and you probably won't be as drained by the end.
At the end of the day though, don't think it really matters. I would suggest spreading out. I'm applying to about 12 firms, 3 offer winter, spring and summer, 3 offer just spring and summer, and 6 offer only summer. So I'm applying for winter for the first 3, spring for the second 3, and summer for the remaining 6. Maximises the number of schemes I could theoretically do, If i were to somehow get an offer for all of them, I could feasibly do 5 (1 winter, 1 spring, 3 summer). If I only applied to summer, I could do max 3, imagine i got 2 or 3 offers though and the dates clashed etc. Applying across all 3 periods gives flexibility. Of course that's all hypothetical and I'd be lucky to get even 1 🥲
Having said that, I'm hoping, praying, dreaming for a winter vac scheme offer from one of the firms I'm applying to. Then I'm hoping, praying, dreaming I convert it. Maybe it's a pipe dream, but I'd feel so unbelievably happy, and more than that just relieved, to have secured a graduate job before semester 2 of second year. Would save doing any more assessment centres for the later schemes, would save me having to do summer schemes or other internships, save me doing applications into third year. Could just focus on enjoying uni and coming out with a 2:1. Fingers crossed 😭
