If your salaries are essentially the same, saving 100% of one or saving 50% of each is the exact same.
I'd beg to differ.
Saving 100% of one salary is not necessarily the same as saving 50% of each, even when both salaries are the same.
In which person's name(s) personal pension contributions are held / accumulated
can siginificantly affect your combined tax liability when it comes time to draw upon your (defined-contribution) pension(s).
My spouse and I both had very similar salaries for 30+ years.
We both saved approximately 25% of each gross / pre-tax salary directly into our personal defined-contribution pension funds (i.e. tax-deferred).
And then we each saved a further 25% of each net / post-tax take-home pay into tax-exempt savings funds (maxing out each of our yearly allowances here too).
(Actually, early on we used some of this net post-tax take-home pay to pay off the mortgage relatively early.)
When we are able to access our accumulated pension funds,
because these funds are split 50% / 50% between the two of us,
we are able to minimize our individual tax liabilities by using both personal tax allowances
without either of us having to make withdrawals that cause us to pay any higher rate tax.