BookShelf or Floor Standing Speakers

Generally speaking  
  

• Bookshelves give better bang for buck (most $1000 bookshelves sound better in their frequency range than towers) which makes sense, especially factoring in shipping.  
• Towers have more bass, varies from a little to a lot.  
• Towers have a bit higher max SPL than bookshelves from the same model line. 
• Bookshelves are more customizable to your listening height by simply buying the correct height stands, some towers may have their reference axis too high/low, which would require tilting and whatnot, which can only help so much.  

Depending on the budget, I usually recommend a subwoofer anyway, so the bass extension benefit of towers is mostly negated, and crossing over bookshelves will add a bit more SPL (unless already maxing out wattage handling). 

     Bass frequency soundwaves  are so much longer than midrange and treble frequencies ( a 20 Hz bass full cycle soundwave is 56' long and a 20K Hz full cycle wave is a fraction of an inch long) and behave so differently in a typical room that I believe it makes a lot of sense to use high quality stand mounted bookshelf speakers for optimum midrange, treble and stereo soundstage imaging and then position at least two small to medium sized high quality subs in the room for optimum bass response at the designated listening seat. 
     I'd suggest two SVS SB-1000(sealed sub) or PB-1000 (ported sub)subs that can be currently purchased for $950/pair for either model.  These are high quality subs that are a true bargain because they perform more like a $1,000 sub from other brands.  Here's a link to the SB-1000:

https://www.svsound.com/collections/1000-series/products/sb-1000

     You can optimally position each sub, in relation to the listening seat by utilizing the 'crawl' method.  Once the subs are positioned, position your choice of bookshelf speakers on stands for optimum midrange, treble and soundtage imaging performance in relation to your designating listening seat.
     The last step is to configure the volume, crossover frequency and phase control settings on each sub so the subs and your main speakers blend together seamlessly as a unified whole.  I'd recommend running your speakers full-range and setting the volume and crossover frequencies as low as possible with the combined sound still sounding very good to you. Remember, the goal is not to constantly notice the subs being active, but for them to become active only when the music recording calls for it.  I can describe a few easy ways to optimally set the phase controls on each sub if you decide to use bookshelf speakers with two subs setup.
     The main issue I have with floor standing speakers is that the bass sections are not independently positioned in the room for optimum bass performance.  These types of speakers are typically positioned for optium midrange, treble and soundstage imaging, in relation to the designated listening seat, and this determines the location of the bass drivers in the room since they are permanently attached, usually just below the other speaker drivers.  This positioning is unlikely to be their optimum positions in the room in terms of bass performance at the listening seat.

Tim

Not to take this thread sideways but what about running the risk of not getting optimal integration with the subs and stand mounts? I prefer stand mounts for aethetics and mobility but I'm scared of never getting subs to integrate correctly for all music.

After reading your thoughts on this, I have decided to go with a large, or full range book shelf.  I have Dynaudio X18 book shelves now, but would like to purchase some better speakers. 

I am convinced to stay the course with bookshelves.  I want to thank all of you who provided some great advice on here.  You saved me a ton of money and searching.

sttt, you might want to take a listen to Harbeth Monitors. If you want more volume and efficiency Klipsch Heresys.