I like the "ow" better. Maybe it's because of my fondness for cows, I don't know.
As to the important of pronunciation (in case anyone asks me), I would recommend trying to get as close to the book pronunciation as you can. Don't worry if you are exactly "correct" (if there is such a thing) in the beginning, you can change your pronunciation when you move to the advanced Latin stage.
Right now just try to be as close to the book pronunciation as you can, making sure that your vowel sounds are all clearly different from one another. If your vowel sounds are not easily distinguishable you will have trouble with your conjugations. (I have to be especially careful with my e's and i's.)
Stay consistent in all of your pronunciation lest you have difficultly with syllables, accents, memorization, and translation.