Well if you are familiar with Kenwoods, I'd go with a kenwood. It will cut out any learning curve, causing less hair loss/frustration
As for the D710A I've only heard good thing about it, so I can't say anything against it, and believe it would serve you well. If you would like to read reviews from actual owners I'd recommend this page.
Kenwood TM-D710A Product Reviews
I don't know anyone with the 72 so I'm hesitant to offer any opinions, but it did score highly in reviews. TH-D72A Reviews
Kenwood TH-D72 Product Reviews
It sounds to me as you are familiar enough with radios that your "why buy cheap and just have to upgrade later when I can learn on one that I will have a while." quote is solid thinking. If you had much less understanding/were a complete Newb. then I would tell you to go cheap.
As for getting to know antennas better I would just spend some time in the Antenna forum reading and getting a bit more comfortable. (I'm a little weak there too, so I don't want to steer you wrong LOL!)