If the price of a 345 is less than a 335, 345 has preference because it is slightly more future proof than the 335 due to its dual 5Ghz capability. Down side is it will require you to upgrade to 8x.
But you will have to check the prices with your Aruba contact. Besides Aruba stratega prices also can differ based on the amount of AP's you order and your negotiation skills :)
335 also supports hitless data and PoE using both ports (active-active)
Not sure about 345 but 335 is heavy (almost 1 kg) and gets warm but with the standard equipped mounting brackets and decent ceiling no issues (have been running 500 of these for 1 year now).
335 can also run with PoE with limited functions.
Unless you are in real need of extra 5Ghz access (you could also add additional AP's)
you could go for the 335 which allows for a more smoother and easy migration. Make sure to upgrade to at least 6.5.x (minimum requirement 335). Once you have a suitable timeframe, you can prepare and migrate to release 8.x.