I don't place a whole lot of faith in basement storage numbers. They can be added up in a number of ways so using them for comparison purposes is pretty much meaningless. What it's really all about is the useability of that space. Counting little corners and odd shaped areas that don't serve a usefull purpose is just tricky advertising. You really need to look at each model to see where that space is.
An example is our Allegro Bus. It had the equivalent footage of a Phaeton yet the Bus had more useable space due to it's use of AquaHot rather than LP furnaces and water heater. Tiffin located the boiler in the middle of the coach. That gave me much more useable space than in the Phaeton. Thedrawback was that the AquaHot is a component that requires regular service and it was near impossible to access. None of that can be seen on the spec sheets though until you start poking around.
I will say that the 43' Anthem is much better than our similar Bus. The basement height is taller and that extra bit really makes the difference in practical storage. Entegra also places the inverters up between the frame rails where they have a zero impact on cubic storage space. Tiffin places their inverter (and their HDMI A/V distribution system) near the top of the storage compartments but off to the side where they limit the use of any tall storage containers. Again, that's not shown in a spec sheet but a hands-on inspection reveals the benefits of the Anthem over our existing coach.
You really need to go take a look and bring a tape measure to have any kind of meaningfull comparison. I think you'll like what you see.