I hear this quite often, that E10 picks up and holds water. I consider that a plus, not a negative.
First lets look at total water availability. Where is it coming from? Leaky fuel caps? Fix them - that affects 100LL ops just the same, so that argument in a non-starter. Humidity from the air vent into the tank? Ok, I'll grant you that one. So if you fill up a tank, burn almost all of it, replacing that void space with outside air - how much water is there? Let's be generous and say you inhale 18 gallons of air (each tank), at say 90% humidity. In flight the water level in the air will be much lower, but you will eventually have to land and the higher pressure and humidity there will be your worst-case scenario, so let's go with that. 18 gallons is 2.406 cubic feet of air inhaled to replaced the 18 gallons of fuel burned. At 86 degrees F (yes, I know, just looking at an average here) air has a maximum moisture content of .0019 pounds of water per cubic foot (commonly available moisture tables - let Google be your friend). That works out to .00457 pounds of water inhaled at 100% humidity, or .00411 pounds at a generous 90% humidity. For simplicity of the next part I'm going to jump to SI units now - that .00411 pounds is 1.87 grams of water, or 1.87 cubic centimeters of water volume. There are 20 drops of water in a single CC, so we are talking about 37.4 drops of water in a worst-case scenario. E10 fuel can hold 0.41% water IN SOLUTION (no separated water, all dissolved). So 1.87 CC divided by .0041 gives us a remaining fuel volume of 456 CC's that is able to hold that much water in solution without separating. That's literally a PINT OF FUEL. How far down into the empty tank zone do you consider to be your limit before stopping for fuel? Because the math says that if you run E10, and have at least a PINT left in the tank before refilling, it's not possible to pull enough moisture out of the air to make liquid water in the tank.
Go ahead, check my math. I'll wait. For reference, 100LL's ability to hold water is about 2% of E10 - which means you will need 50 times as much final fuel volume to hold that water in suspension - just over 6 gallons in this scenario. This scenario also ignores the fact that some of that total moisture inhalation is mixing with the fuel during flight and being burned through the engine - so the final resting volume of water available prior to the next fillup is, in reality, much less.
I know I have 1620 hours and 8 years running E10, and I've never found any water in my sumps.