I noticed the Lew's reels have deeper spools on their cranking models. Is this desirable in a reel for deep cranking?? Is it because you may want to use heavier line and it can hold more that way??

I fish deep crankbaits a lot. I use them in wood and a lot of rocks. So I am constantly having to re-tie. I may have to cut off a yard or more each time. Within one day, I may lose 20yds of line. If I am using a reel that only holds 110yds of 12test,that would shortly dwindle away on my casting distance. A fuller spool will cast much farther than one thats not full. If you are spooling your reel in a day or so after cutting away frayed line you'd be happy with the bigger spool. If you don't bang up against cover and have to retie often and your not fishing big 1 ounce plugs and casting long distances, it would probably benefit you to have a smaller spool and just save yourself on the weight of the reel.

Another advantage to the deep spool is that the weight of the line adds mass to the spool which adds casting distance due to the inertia. On the opposite side a shallow wiffle spool is light and will start up easier to aid casting light baits.

Many don't know it, but the BPS PQ 5.2 and 4.7 ratio spools are also deeper than the spools on the 6.4 and 7.1 ratio reels. I use 17lb mono on my 5.2 reel so the added capacity is beneficial. However, I use 10lb YZ on my 4.7 reel and it's really excess capacity to my needs - although I guess there is merit to the added mass on the spool to add casting distance as this reel is on my deep cranking rod.

In any event, this perhaps is another indication of the family relationship between certain BPS reels, and the Lew's reels that are assembled in the same factory in Korea...