You have a concrete subfloor. When considering the choice of floating your hardwood floor or directly gluing it down to the concrete subfloor, the following list of pros and cons should help you make the right choice.
The first thing you should do however is check with your strata if you have one. Quite often there are rules in place that govern the method of hardwood flooring installation.

Lets start with  the floating floor method of installation. 

The term 'floating hardwood floor' refers to the method of installation.  A floating floor rests on underlay and is not fixed to the substrate or subfloor. Essentially, gravity holds the floor down.

Floating floors
1. Less expensive than the glue down alternative due to less installation time and minimal adhesive cost.

2. Easier to install especially for the 'do-it-yourselfer'

3. Quieter for your neighbours below. The two air pockets between the flooring and underlay and between the underlay and the concrete break down sound transference better than when the floor is glued down.

4. A finished floating hardwood deflects or 'gives' sightly when walked on. This makes living on the floor easier on your legs and back.  Don't worry, the movement in the floor is to be expected because the floor rests on a soft underlay however the amount of deflection must not be excessive. 1/8" is acceptable. Your concrete subfloor should be leveled properly by your flooring contractor. More information can be found here.  You should have no sudden drops or ridges in the concrete before you begin installation. Inadequate or poor leveling will leave excessive soft spots which can cause movement in the floor that may lead to breakdown later on.

5. Soundbarrier. There are many sound-rated underlays on the market, each with their own pros and cons.
Look for the IIC rating on the product (Impact Isolation Class). This rating indicates the amount of sound transference through the concrete subfloor to the space below in a test setting.  The higher the IIC number the less sound transference.  Various products on the market offer an IIC of between 60 and 73 and are priced accordingly.  The best value, in my opinion, is about 70.  Most sound rated underlays should cost you less than $1 per square foot.

Glue down floors
1. With this method of installation, the finished floor feels stronger and more solid underfoot. This is because the floor design doesn't allow for movement or slight deflection. 

2. Noise. Imagine the sound of a foot step on a glue down floor to be a 'dull thud' as opposed to a brighter 'clack' sound that comes with the floating floor design. The sound of the floor is generally quieter to live with because less noise is reflected back into the room you are in.

3. Expense. Glue down floors are more labour-intensive to install and the adhesive alone will add $1 plus to your cost.  If a sound barrier is required, then it will need to be glued to the concrete first, adding yet another $1plus per square foot for the adhesive PLUS labour to install.  You can see how the cost quickly adds up.

4. Removing a glue down floor is a tough job. The adhesive is very strong and designed not to let go.

5. Gluing hardwood to a concrete slab on grade requires a special moisture barrier (the grey product to the left of the glue bed in the picture). This will add another $1 plus labour to install, whereas a moisture barrier for floating floors is no more that  $.10  per square foot.

So that covers the basic pros and cons to consider when choosing a floating versus glue-down hardwood floor.

I'd be interested in hearing what your experiences have been with installations.  What were the biggest challenges you ran into?