Which is better. Stainless Steel Grab Bars for a shower or Chrome Bars? I am having my tub removed and the section made into a shower. Thanks

Something not slippery, that you can get a grip on.

Stainless is preferred but is more expensive.
And yes, get the kind with hatch marks for gripping.
Plan the position and angles very carefully, and add extra framing behind the wonderboard, and keep a map of where it is.
If vertical, totally vertical.
If horizontal, a slight angle is good for different height people, but not vital.
Angled ones are most common above tubs and next to toilets.