Very few people use this anymore as woofers now have alot of mass that simulates this style. Back when I started a single 10 ported was around 3 cubic feet, maybe 1.5 sealed, so isobaric isn't really usefull nowadays.

 

Back in the day, power was at a premium as well, so they made woofers as efficient as possible, with light cones and voice coils. When power became cheap the car audio industry realized that if you increased the mass of the cone and coil the sub would work in a smaller box but require more power, a trade off that survives to this day.

 

the main advantage of isobaric is the addition of an extra motor assembly, spider, surround, magnet etc. you get 2 motors working to control excursion, the sound will be tighter and usually deeper bass due to better cone control at lower frequencies, the debates have gone on forever which is better compound or push pull, i prefer compound because of potential pole vent noise, but both sound great, better than average imho

 

You listed the advantages which is good, but I will list the disadvantages. Which are lowered sensitivity, and you are paying for two subs and getting the output of one sub.