I am in the same situation, I love the looks of the 718’s, so clean looking. I am going to get fit next Saturday with a Titleist rep at our local Golf USA with a Trackman and try out some Tmb’s for the longer irons such as the 4 and 5 iron. Will test them side by side....

718ap2 all day long, I even thought the 714ap2 irons were better than the old 716ap2.

Each to there own,
go get fitted at Titleist and see what ones work for your swing.

The 718 AP irons are all gorgeous. If you buy off the rack from a store, probably not much difference. Going to a pro shop and find the right head and shaft for your game could be dramatic. The retail set and the custom fit set are essentially the same price per club. Quality clubs aren't cheap, but the correct fit is priceless.
I went from AP1 with graphite to AP3 with metal shafts but only because I gained almost a whole club of length.

Proper fitting is the key here. I had 716 AP1s, and was also conflicted because the 718 are so nice. I was drawn to the AP3s on looks, but wanted to get fitted to see if they were worth it. Had I bought a set off the rack, with the standard shaft that the box stores have in stock, I would have been disappointed. The stats were relatively the same, and I would have spent a ton of cash on clubs that were "purdy". Switching to a different shaft (one of the many stock shafts Titleist offers) made a huge difference, and I was able to justify the new purchase. Not only do I have a set of the best looking clubs on the market in my bag, I am also seeing lower scores.