What's better aluminum tape or mesh tape w/mastic for sealing dryer vent?
Using mesh and mastic is very important if you want to seal all of your HVAC runs in a house.  Tape simply doesn't adhere good enough over time to limit the tiny holes they are trying to cover.  It is a big deal to seal a house up right because a properly sealed unit can be 10-20% more efficient - and that is a lot of money for the 2-4 hours it takes to seal it right.

However... your dryer is not part of your HVAC system.  It is just a vent going to the outside of your house.  The tape is just used to make sure there is a smooth transition so that nothing get caught in your connections (you should not screw in your dryer venting runs to each other).  Therefore aluminum tape is the way to go because when you want to clean out your vents you can untape them and retape - hard to do this with mesh/mastic.