how different? it's still the same OS. spec wise, it's also similar to Air, MBP 13.
Some are price conscious are unsure about taking the next step. A budget mac os experience opens a window of opportunity for them to try.
You say the Mac Mini Spec is same as MBA, I was comparing with the iMac. In the very first post from TS, the discussion is with regards to between Mac Mini and iMac, so it will be more appropriate to just stick with these 2 in this discussion.
The user experience of Mac is more than just a bunch of equipments, if that's all you count Mac is on, then it's not the Mac experience. Of course, it depends on what one wanted after all.
The beauty of Mac is a holistic experience from the beauty of the machine all the way into the beauty of the OS. That is the reason why I was attracted to it more than 10 years ago when OS X first launch. Obviously the experience of the OS on a Mac Mini will not be very different, but it could be given the Intel HD4000 isn't exactly one would call a wonderful graphic processor. iMac has a discrete GPU to pump the required graphical experience that one would get out of the machine. This part, I'm sure you would already knew.
Next is the integrated experience of a iMac without cabling all over the place, the nice aluminium beautiful large display right in front of the user. Tell me this has no difference to a Mac Mini with a DELL display, hard to believe. Of course the Mac Mini user can go for the Apple Display which would easily achieve the same thing for a much higher price tag, that's another avenue to proceed, just not ideal.
All in all, I think those that supported the iMac as a better entrance into the Apple world come from a holistic approach looking at how a beautiful machine makes you want to sit right in front of it daily and work on your stuff. Where else the Mac Mini serve a different role in the product line for the purpose of a less powerful unit that can hide away, but I doubt, one will call a 3rd party display a good user experience to convince a newcomer into the community.
Your concern about the price tag being hefty is valid, but likewise, if you spend $600 less and did not get the WOW experience that $600 more could get you, then you lose more than just $600. It's not like after you spend on the Mac Mini, and the next day you love it and you would get a iMac immediately, basically the user experience is locked in to what Mac Mini can offer. You can say Mac Mini is enough, but is it true for everyone ? I don't know.
But from my perspective, I know and have experience what iMac can impress to a new user as oppose to what Mac Mini can do, that's why under no circumstances would I recommend Mac Mini as the first hand experience.
Well we can go on with this debate with no conclusion. There is no right or wrong approach, just a matter a preference. I suppose I'm just bringing out what could be missed if the alternative is taken. After all it's TS's prerogative.
My view is if one want cheap, go use Windows. Apple is not a cheap product, but I think existing user will know what is the value of Apple in this IT industry. The effect it has on users are like Macdonald. After 3 decades selling more or less the same thing, yet people still welcome the food. It's not the food that is fantastic, it's the atmosphere and the ecosystem. Apple is a premium product, but its one that will make you feel that you have made a good investment.
If you just want to play games and use some products that only exist in Windows, don't come aboard. If you want a powerful OS that does more than just a pretty skin, you have found one. That is the main reason why I have been using it for 10+ years.