We've stayed at Pop, ASM and POR and unless there was some incentive (like free dining) being offered to stay at a Mod I don't think I would pay the extra to stay at a Mod over a value, yes the rooms are slightly larger and you get an extra sink which I suppose is a benefit if you are a family (it's just the 2 of us) but I think the values in their own right are just as nice as the moderates. The moderates have lovely adult landscaping whereas the values have in your face fun landscaping. The mods also have a table service restaurant but that's never been a deciding factor for us either as we prefer the restaurants in park or at the deluxes.
I would say the biggest factor is personal preference on the theming of the resort and weighing up the extra cost if that is the type of theme you prefer (as usual it also depends how much time you will spend in room and resort) and also if the table service restaurant and slightly larger room are important to you.
We decided on All Star Sports for the first part of our May trip as the first week will be all about the parks so went for the cheapest option and as all our dining is centered around the parks, resort dining wasn't a factor and like I said there is just the 2 of us so room size isn't a factor and we find the value theming fun.
I do like the moderates I'm just not sure (for us) that they warrant the extra cost over a value to stay there (excluding any offers that are on)