Keep or Sell 24-105 f4 for 24-70 f4

There are transaction costs associated with buying and selling.  Unless you've got a compelling reason to switch, you're just giving money to eBay and shipping companies.  Also, after you sell the 24-105 but before you buy the 24-70, what will you take pictures with?  Take some time, read the reviews, consider the added expense, and then make the switch if you still want to.