theoretically yes since interest can be offset against income to lower your tax bill.
Everything else being equal (such as interest rates etc..), with a capital repayment, your interest payments drop over course of time and so this offset reduces (and hence your taxable profit go up which is not good).
there are of course many other areas to look at such as interest rate on an interest only mortgage vs a capital repayment mortgage, your risk tolerance (since with interest only your balance never drops so you aren't building up a capital cushion), what you will do with the money you save on a monthly basis going interest only vs capital repayment.
professional advice recommended!