I personally throw a combination of 15 & 16. With the 15, I tend to generate a little more mph, maybe 1/2 a mph with the same swing and I've learned over time so that my balance is not affected changing back and forth. Some other bowlers say, changing back and forth affects their timing and balance.
As a new bowler, I would not recommend doing what I do. I've been at this for almost 40 years.
As everyone above as said. Visit a local pro shop and have a ball custom fitted for you. It will make all the difference. It may also feel weird at first, since you will be used to the big loose holes of house balls.