Like somebody else said, a driver generally specified as a "car audio" driver is usually a 4 ohm driver with some weatherproofing. Some may have a higher Qts, but not always the case. Like all specs, Qts can be misleading, and not always indicative of how a driver will react in a car.
Off-axis response is more a function of the size of the driver than anything. The surface area of the cone will tell you when the driver will start to beam, i.e. localize more on-axis than off. That being said, a 7" driver will never perform at 5000 hz off-axis as well as a 4" driver. So, when I hear that a 7" driver has great off-axis response, as opposed to another driver I have to say that it's probably going to have the same difference on-axis, and will generally manifest itself as more detailed midrange frequencies to begin with.
If you do have a 7" driver that has actual better off-axis response, i.e. plays flat to 2500 hz at 60 degrees off-axis as opposed to 2300 hz off-axis at 60 degrees, then I'll say that the cone has less surface area and will probably not extend as low as the driver with worse off-axis response. It's all give and take.
The Exclusives are a great driver, with great midrange clarity and a little better off-axis response. However, as stated above, what they gain on their top end, they sacrifice on the low end. If you're looking for a 5.5" driver with some midbass thump then you may be disappointed with the Exclusives. If you are running active crossovers with 18 or 24 db slopes, the Seas L14 or L15 is a great driver with very good midrange clarity, and some good low end thump. However, being an aluminum driver they are subject to nasty cone breakup, and you need some hefty crossover slopes to defeat it, and a tweeter than can extend down to around 2700 hz, which the Cal27 should do, then the L14/15 is hard to beat for a 2 way 5.5" midbass driver. The Exclusive is a much easier driver to work with though.