A good friend of mine in high school had Large Advents and every time he came over to our house and heard the 4’s—less than half the size of the Advents and half the price—he’d say, “It’s not fair! It’s not fair that they sound so good!” So my Dad and I called the 4’s the “Not fair” speakers from then on.
A familiar story. I had sold my AR-3a's back in 1977 because I got tired of shipping them off to AR to have the tweeters replaced (I was seriously underpowering them). A pair of large Advents replaced the 3a's as they were more "robust" when fed a diet of clipping distortion. Of course, the 3a's sounded better, but it was a compromise I felt resigned to. The gist of it is that I could never understand why my good friend's AR-18's sounded so much better than the Advents - especially in the upper midrange where the Advents were decidedly harsh.
Fast-forward to 2004 and my renewed interest in vintage gear. The first thing I did was get a pair of AR-18's and refoamed them (the Advents were in need of a refoam and had wound up by the curb several years earlier - Advent lovers, don't flame me - I didn't know refoams were a possibility back then!). Since then, I've happened upon a pair of AR-3a's (hey, they came back!), AR-7's and AR-17's, all of which I've restored.
I really have a soft spot for the AR-7's. They just look so good, like a pair of mini- 3a's. But based on my own pink noise tests, the AR-17's and 18's are more neutral sounding than the AR-7's, which have a mild peak centered around 1.8k. The 17's and 18's sound almost identical (they should - they use the same drivers), but the slightly larger cabinet give the AR-17's the edge with an extended bass response rivaling an AR-5 or AR-2ax.
So my choice, based on my limited experience, would be the AR-17 for best 8".