Legs would be good too, no doubt. We consider them often. I suppose as long as we're discussing air vs leg, we should lay out +s & -s. Again-the original poster question is starting from almost zero.

You mentioned positives of leg. I don't think you mentioned any downsides. Here's a few we considered.

Cost....I know what we pd for air and leg to do same was a lot more than 2x. The only concrete for air was a little pad about 3'x4' to sit it on. The rest was done in a couple days by welding tube.

Tubing....since air can blow uphill-sideways-downhill-around a corner, it's pretty versatile. I think grain can only go downhill from leg, unless you involve more drag augers.

Sizing. Again-you can buy a slightly bigger air system than you need now & upgrade (or not) later simply by buying up to larger motor...assuming your electric will handle it. Not sure that's possible w/leg.

Filling-you're right about filling. But, one of the disadvantages I see about local legs (the commercial ones you mentioned also) is capacity @ time of install vs 20-30 yrs later. A few yrs back, most here filled bins w/10" auger, now 13" @ 10,000 bu/hr isn't uncommon. I think it would take a pretty good FARM pit & leg to handle 10K/hr, wouldn't it? Keeping pits dry of water is problem in NE IL. Now, I can also tell you that in 10 yrs or less, 10kbu/hr will  be too SLOW. I'm guessing we're headed to even bigger auger or fill device. That's OK, they're somewhat portable & easily upgradable. They have some used value also. But-seldom do I see legs upsized from install.

Used value-not sure of used value of legs. Is there a market for that? Good augers can still be sold/traded easily almost anywhere...they're mobile. Same w/air system. I could probably have our air system dismantled & laying on the ground (not broken either) in a day.

Location-once you get a few yrs down the road & discover you should've located something differently-how easy is it to move the leg? Air isn't exactly on wheels, but it's not even bolted to the pad. 

Maintenance-I assume I'll do 99% of maintenance on air system standing on the ground. I assume most legs have a ladder & catwalk for upper end maintainence. On an air system, we have blower & airlock to maintain. That's about it. I'd sure think there's more to maintain on leg?

Weather. I've seen a few legs get torn down by storms. I guess it's possible to lose some tubes of air system....but usually not the whole system is wrecked.

Now-unloading those bins is another problem for air...no doubt. I don't know anyone using air to load out. Again-we use our augers.