I can 't comment on the PLUS series as you find them from the counter right now, however I can comment on the series as they were back in the late 80 's when I purchased many of the 10+, 15+,20+ & 30+, I see no changes in the design but I can 't judge them by sight through an on-line catalog, it 's been more than a decade that I purchased a lure from that series.
They were good ( mine still are ) baits specially because back then right at the dawn of the age of the dinosaurs when I bought mine no other manufacturer offered bait that could dive at those depths, they are very convinient for me since most of the lakes I fish on a regular basis are built on steep sloping canyons where the lakes can reach 300 ft in depth with very few areas that you could call "shallows" and filled with very clear water where you can see down 20-30 ft. In order to reach those depths ( or if you want them to do the "stretch" ) you need to fish them with thin line 10 lb test or less. Excellent bottom bumping baits, got a 8 ft deep target ? grab a 10+ and slam it with the bait, scratch the bottom and lift some silt.
They are extremely durable ( mine have taken quite a beating through the years ), the bill is made with a very tough plastic that takes the punishment without having to worry that it may break ( like the Rapala DT ) shaped like a spoon, the bait is made of tough plastic and has 2-3 chambers ( depending upon the size ) with 2-3 large steel balls inside ( 1 per chamber ) that give out a very audible clacking noise. Opposed to other baits where the overall size of the bait body is large in this ones it 's not, the bait is as large as the bill. The hooks on mine were good quality although they needed a little honing to make them razor sharp. They are not the most wrist friendly crankbait around, they dive steeply and have a great deal of water resistance so they need a low speed reel to crank them in otherwise they feel like reeling in a bucket.