When designing for mobile, should one prefer buttons over text links whenever possible?
I'm guessing buttons are better at encouraging tapping, whereas text links are increasingly becoming associated with static content?
From Fitt's law, a button is better than a text link, because a button is bigger than a link, so a user use short time to click it. Moreover, it is hard to select small area on a touch screen, because a tip of a finger uses wide area, so the system can identify which area a user would like to touch.
From my answer, I assumed that a button is bigger than a text link. However, if a text link is as big as a button, a text link and a button are similar. Thank Mohit for pointing out my error.
I don't have any theoretical background on this, but from the experience of doing mobile app design from past 3-4 years I can tell share that
I would use a 'center' aligned button to indicate user the main action of the page. Button background color needs to have contrast in comparison to rest of the page's color scheme.
I would put a chevron icon image at the right end of the list item to indicate that there is an action on this.
If the number of tab items are 2-3, then I would use text button. Else, I would go with an Icon based button
Color of the text will be blue (to indicate link), with an underline.
The difference between links and buttons has been getting blurred for a while now, many nav items are technically links but look more like buttons.
On a touch screen buttons (or button-like links) are easier to press than links, and that behooves us to make commonly accessed clickables to be buttons or button-like.
Not just buttons, buttons having appropriate hit area should be designed for mobile due to the touch aspect involved. User interface guidelines defined for all the major Mobile platforms always come in handy for this purpose.
Coming to the crux of the question, text can very well be used as "buttons" provided it is
Informed use of different colors is highly recommended for differentiation aspect of the interface. Use of too many different font-sizes is highly looked down upon as it ruins the usability aspect.
Since Windows Phone is a brilliant example of well informed and designed typography, you might want to read upon its User Experience Design Guidelines here: