Both are quality pistols and both will be more accurate than your ability to shoot. You really can't go wrong with either. Just like we all come in different shapes and sizes, each of us have unique preferences for how we shoot. Try both and pick the one YOU shoot better with.
FWIW HK is notorious for a high handed approach to customer service (primary desired customer is LE and Military, not consumers). Walthers are warranteed by S&W.
HK's are lusted after by Tom Clancy fans.
Walthers are considered cool by James Bond fans.