That's a really subjective question!
It depends a huge amount upon your height, seats, seating position, all of which can influence how good a view of the instruments you get even with a stock wheel. Generally speaking reducing the diameter of the wheel inherently means you will lose some visibility of the dash instruments, it's a question of what is most important to you.
Because of my height I have always had a hard time seeing the speedo so I mounted a speedmeter right on top of the steering column so I can see it. It looks as ricey as sh*t but it makes driving so much more comfortable for me.