You know stock size is 295/45/20 yeah?
295/45/20 is 30.43" tall (30.9" tall according to Pirelli spec sheet)
295/40/21 is 30.29" tall
295/35/21 is 29.13" tall
The percentages you quote are close, but you have it the other way around
I suggest either researching the manufactures specs or using a tyre size calculator
The only benefit the 35 will have is its a common O.E tyre size and easier to get, but much smaller in diameter than the stock tyre size and you may find it hard to get a 110 load rating in the 35 profile
Seek link below