New Cards
Assuming the shoe game:
IF, and this is an important IF, the cards are thoroughly washed, then new cards are no different than old cards; sometimes we win and sometimes we lose. On the other hand if a "weak" wash is performed, it might be better to wait for a couple of shuffles before playing the cards. Just take a careful look at the wash being performed. You'll know quite readily IF the cards are being mixed well. IF they are, go ahead and play. Don't worry about it. If you have any concerns about how well the cards are mixed, then come back after a couple of shuffles have been performed.
This is strictly my opinion on this subject. I have played new
cards often and have generally mixed and inconclusive results. In short, sometimes I have won and sometimes I have lost.
best of luck
-- oms --