I'd say multiple internships in the financial services are going to be way more beneficial than a cadetship at an accounting firm. End of the day when you're going for a job in the financial sector you'd rather have relevant experience under your belt as opposed to two years of professional experience as a cadet in an industry that may not be relevant at all.
That being said it can also come down to which line of service you work in as a cadet. If you're applying for a job in the financial sector, experience as an assurance cadet in the financial services will probably carry more weight than a cadet who has worked in tax.
I only partially agree with this in principle as it definitely varies in terms of what's "better" to help you get into the job you want, and if you're planning to only do it for a year or two in an undergraduate role, then realistically it's how good you are at spinning your experience as opposed to the substance of it all.
When you say (etxpy) you want to work in financial services, what do you mean by this? The industry is very broad (you've included banks, insurers, PE funds, etc) and so are the individual roles... and that's before we even consider the blurring of the lines between various previously discrete sectors. You did suggest IB internships in which case if this is the exact path you plan to go down, then even getting one IB internship puts you in a far better position than doing the cadetship program, but for generic broad FS roles whether it be front or back of house, and across various organisation types, or even up and coming disruptors, then I'd say getting a broader range of experience is probably more beneficial.
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