Then there is that "other" factor,
Just because it is a tower does not mean you get deeper bass response--depends on the design. For instance, a JTR 212HTR is a "tower" speaker at 40 inches or so tall and around 15 inches wide--very "tower-ish". However, the specs are 70 Hz to 24 KHz and it has two 12 inch woofers and a coaxial compression driver for a three way system. The point of that design is to make it a "tower" to gain massive efficiency--data-bass measured the 80 to 350 Hz efficiency at 105dB at one one/one meter.

It is all part of Hoffman's Iron Law, little, low frequency or high efficiency, pick two and lose the third. The JTR lost the low bass extension but has incredible efficiency.
In reality, many people use multiple subs so choosing towers that are more efficient allows higher SPLs of reference levels in larger rooms where it is required. Towers can be that size to either gain lower bass extension, gain much higher efficiency or a mix of both.
Now for a lot of "towers" I see now that seem to be popular is their bookshelf drivers mated with more or slightly larger woofers. That design severely limits the tower to being a bookshelf with better bass (but not as good as a subwoofer) That kind of thing I avoid, get the bookshelf since the mids/highs are limited anyway and pick up an extra sub or two from the cost difference. It all depends on the design, for me I expect more efficiency from a tower, more power handling and less distortion compared to a bookshelf. Sadly, the style is skinny towers with a bunch of wee little woofers which look stylish but when used with subwoofers--a waste of space compared to the bookshelf version.
For the record, I use subwoofers and have used them for decades because it works better for my use and my preferred music. My present speakers are "large bookshelves", at least that is the lie I tell my wife. 20" H X 12.5" W X 12.7" D. They have no deep bass but the mid-bass slam will be felt very easily. My 10" woofer is for the midbass slam and at 98dB 1w/1m--no problem rolling right past reference levels even with basic AVRs.
So as with most things--it depends. If you can, look at other towers with higher efficiency as an option and leave the deep stuff to the drivers that are designed to perform--the subs. Good luck and I hope it works out for you.
