If you are planning to replace your bathroom faucet, I hope this article serves as a great resource or primer.
I wrote it so you may select the one

• That you like and suits the theme of your bathroom
• That is correct for you sink

The key factors to keep in mind are:

• Price and how much of your bathroom DIY budget you can spare
• Style - traditional, contemporary or transitional
• Finish - Chrome, SS, BN, ORB, etc.
  
• Material
• and type.
  

The first thing to learn is the different types of bath faucets and how to identify them.
This is key because you can decide which one appeals to you and also which one you have currently.
You will have to stay with the same size of faucet, unless you plan to change your sink too.
So here we go

1. The Single Lever/Single handle: These are easily identifiable with the single actuation handle that controls the flow of the water as well as the temperature.
   They require only one hole drilled into the sink and can hence fit into any sink that has a center hole.
   Some single lever will have a 6" trim plate to cover the holes drilled for 4" center set or widespread hole drillings.
   
2. The Center Set Faucet: This type of faucet has its spout and handles mounted onto a 6 inch trim plate in a neat compact design.
   It is great for smaller basins that usually come with the holes pre-drilled.
   
3. Widespread: This is my favorite type of faucet as it gives industrial designers and engineers the greatest flexibility while designing and hence the a lot more variety for the end user.
   The hot handle, cold handle= and spout are separate pieces and when mounted you can see the sink surface between them.
   The widespread faucet itself has two sub varieties:
   • a.
     Mini: The three separate pieces are mounted into three separately drilled holes.
     The distance between the hot and cold handle holes is 4 inches
   • b.
     Standard.
     Same as the above except the center to center distance of the hot and cold holes is any where form 6 to 12 inches (typically 8 inches).
     It also allows for the pieces to be arranged in a circular fashion to follow the shape of the sink.
     
4. Wall mounted: As the name suggests this faucet is hard plumbed into your wall and covered up with dry wall or preferably a tile back splash.
   Often used with vessel sinks and retro styling.
   Our advice...
   if you want this type of a faucet, call a professional plumber to install after selecting the one you want.
   
5. Vessel faucet: Used with vessel faucets and easier to install than wall mounted faucets.
   They are usually single lever / single hole faucets characterized tall spout.
   Make sure it reaches at least 3 inches above the sink and sticks out almost to the middle of the sink.
   
6. Waterfall faucets: These are relatively newer type of faucet and allow the water to cascade down in a non-aerated flow.
   Usually made of glass, they provide a unique contemporary look.
   Make sure they are practical enough for you.
   

Now that you can differentiate between the types of faucets and can identify the one in your bathroom.
Lets read a bit about the materials they are made off.
These are usually Cast Brass, Zinc, and Plastic.
Brass is the most expensive and probably the most durable.
If you are going to use the faucet for more than 15 years go for brass.
Zinc faucets are the next most expensive and is also a great material.
It is bit more susceptible to corrosion than brass, but should last at least 10-15 years.
The truth is once a faucet is installed it is difficult to differentiate between brass and zinc (the main difference being weight).
Also keep in mind that most faucets from reputable manufacturers have to pass the same rigorous tests for lifecycle and also have to meet agency regulations (usually CSA.
or CUPC).
Further a lot of faucets are made with just zinc handles and a brass body or vice versa to get the price down.
Finally we have plastic faucets.
Once again they also have to go through rigorous testing and contrary to popular belief are pretty durable.
Here are my thoughts on durability, metal will perform better for the physical stresses of turning your faucet on/off, however plastic is definitely more resistant to corrosion(i.
e.
it does not corrode).
With modern plastic faucets it is difficult to differentiate because of the quality of metal finishes they plate plastics with, the giveaway is weight and the temperature (plastic will not be as cool to the touch as metal).
After that all is left is too choose the finish(chrome, stainless, brush nickel, oil rubbed bronze etc.
) and style that matches your bathroom.
Hope this helps, Happy shopping and renovating!