Assuming you don't forget to redeem it before it's too late. They have short expiration dates and if you slip and miss the expiration date, you're out $25 instead of having an extra 25 cents.
So if you're organized and never forget, yes, the VVs are a better savings and more versatile. The Walmarts are slightly more expensive (only 12% off vs 13% off), but have no expiration date, and yes, you're locked in to Walmart. But there's plenty to buy at Walmart/Sam's Club, so I'm not worried about never using it all up.
One last caveat - if you use most of a VV's value, it can be a pain to find a way to spend the entire balance. Not impossible, just sort of a pain.