I'm going to have to say that floor standing speakers usually have more bass and can sound fuller. The additional cabinet volume can also deliever deeper bass.
But it is going to be personal preference.
Depending on the size and hardness of your room that may or may not be a problem.
Budget speakers tend to have less bracing, but also tend to have smaller dimensions whether they are floor standing or bookshelf speakers. As such the drivers are smaller, and the cabinet does not require as much bracing.
Some believe that smaller speakers are more punchy and controlled. I cannot comment from experience on this. As for the top end/treble, if two speakers are using identical tweeters positioned and mounted correctly, there should be little difference at the budget end of the spectrum.
I use bookshelf speakers, as I need the portability. However, I do not recommend them over floor standing speakers, and this is why...
Bookshelf speakers often end up on stands, thus they do not save on floor space. Unless you are going to place them on a desk, shelf or wall mount.
Any speaker with rear firing bass ports will more than likely, need at least 15cm or more of space behind it, so expect it to eat into the room (I have about 60cm of space behind mine). I've found that the majority of speakers tend to use rear firing bass these days. The response frequency for bookshelf starts audibly higher than floor standing, but finishes around the same place outside of the audiable range. I.e bookshelf 50hz-29khz, floorstanding 42hz-29khz.
My advise is to demo the speakers you are looking at with the amp and speaker cables you intend to use. Most HiFi shops will set up the speakers for you to listen to with equipment identical to your own if it is in stock, or let you bring your own with you and hook it up.
Amps, Speakers and speaker cables do need a little bit of matching to sound great. I didn't believe this till I found out the hard way (several hundreds of pounds wasted), that not all amps can control all speakers well, and some cables will for one reason or another sound a little better. Smaller drivers are usually easier for amps to control.
As for mains cables the jury is still out, I'm trying a wired world stratus 7 at the moment, and the sound actually sounds worse to me than the stock power cord. I'll order a wireworld aurora 7 next month and I see if this is any better.
I consider my system to be at the lower end of middle or the road, or the upper end of budget depending on how you look at things. But I would recommend that you budget your speakers to be 3-4x more expensive than your amp, and remember to budget for Speaker cables and interconnects.
Take your time matching your speaker to your amp. You are the one paying for it, and will be listening to it. I spent two hours in the show room with my amp, cables and source and still left empty handed. I later decided on my speaker which I am very happy with.
I do not believe in paying over the odds, so try to bargain with the sales assistant if you can. They are expecting, and even in the UK big HiFi chains will let you haggle. I also believe in being happy with your purchase, it's your hard earned cash, so please please demo what ever you want to purchase first against items you have no intention of purchasing. You might be pleasantly surprised.