As a PP has mentioned before- worth is a completely subjective term. What would be a reasonable charge for some is budget straining for others. And you do not mention in your OP how long you are staying.
Frankly you couldn't pay me to stay at a value, and that again is a completely subjective thing, but I'm happy to pay for a mod. We really value the extra amenities that the mods provide, especially the extra square footage in the rooms. This becomes increasingly important as the kids get older (and bigger!!) Again, I don't know the specifics of your family makeup, so it's hard to say how much this comes into play for you.
The only thing I could recommend is to go with whichever resort you are more comfortable with. If it means not fretting about expenses for the entire trip, then stick with the values. If you can manage the mod without financial hardship, then by all means, switch over to the mods.