Most of the time, the actual loan rate (APR) you might be given by different lenders won't vary all that much. As there is a lot of fierce competition between lenders who want your business, they all know that the APR is probably the most important part of their advertising and marketing strategy when it comes to potentially "luring" a customer to check out their finance packages, so you won't find too much difference between them, though they will vary to some degree.
But while interest rates might not vary that much, lenders' fees can vary a lot. These fees are often "buried" deep in the terms and conditions of a loan agreement, so it's important to be aware of these extra costs and be very careful to ask all the right questions when you go to a lender for money. Early settlement fees, payment protection insurance, and other arrangement fees can make one loan quote much more expensive than another, even if the APR makes it look like the two lenders should be able to give you almost identical quotes.
Most reputable lenders will explain any extra costs to you in plain English. However, before you sign on the dotted line, you should make sure that all extra costs and the total cost of the loan are written down. Make sure you ask about any fees you don't understand and ask that they be written down and explained in plain English. Some lenders may even be willing to let you off the hook for the fees.
Some lenders have also started to focus on certain types of borrowers. For example, if you have bad credit, you might be able to get a better deal if you get a loan from one of the lenders who specialises in helping people with bad credit find the best deal.
Take your time and do your homework first. That's the key. Don't rush into signing anything until you're sure that the "bottom line" of any loan proposal gives you the best deal and is tailored to your specific needs and circumstances. Review loans carefully, and if you're still not sure, talk to a free independent finance broker. They can often help you find the best deal at the lowest cost.