I have, use and like both.
The No 50 anti-aging collagen veil primer, looks like a white lotion. For me it's a good all around primer, has a smooth silky slip, leaves my skin smooth and provides a good base for foundation.
The Feel the moment anti-aging ultra hydrating sensory awakening primer serum, looks like a clear thick gel/serum. This one is very hydrating. I use 1 -2 drops for my face and neck. After applying, I brush my teeth to allow time for the product to absorb into skin. You need very little of this product and you have to allow time for your skin to absorb this product. The Feel the moment does have a distinct fragrance which dissipates. If you are sensitive to fragrances this product might not be for you.
If you have the opportunity and access to an Ulta store I would go there and try the products. At Ulta the No 50 is $48 and Feel the moment $38.
bnf46, If you have further questions feel free to ask.