It's a broad, sweeping statement but carriers are not all the same. The carriers have different business models, practices, coverages and technologies. As a consumer, we have the advantage of choice but with so many different carriers to pick from, sometimes this feels a disadvantage!
This article is to help you best select a carrier and my first golden rule is coverage. You may have a fifteen year history with a particular carrier but if you no longer get reception, it is probably time to change.
The coverage question used to be simple. Either you had service or you didn't. But in these days of 2G, 3G, 4G networks, plus add on services such as WiFi, it needs a careful look.
You don't need 3G or higher networks to make and receive calls, texts and emails without attachments. If you need plenty of data I'd recommend using a carrier that offers 4G connectivity.
Linked in with coverage is reliability, which is difficult to judge. There are many components between the carrier and you, including the device, SIM card (if applicable), local and national infrastructures. People you know may belittle a particular carrier but they may be using faulty equipment. It's possible to check up on dropped call and data speed statistics – check with each carrier, but bear in mind that their marketing departments will do their very best to flatter their statistics.
Following on from coverage, many people are price sensitive. We want as much as we can get for as little as possible. Do check carefully the features and benefits; having more minutes is great but less desirable if you occasionally go over and the rate is very steep. Carriers especially like to present customers with high looking data allowances but slap on expensive overuse clauses.
Sometimes, the little extras you get with a given carrier are worthless and sometimes they're handy. In the UK, most carriers give free WiFi access in the London Underground. I travel on the Underground enough that I use this, but not enough that I'd miss it if I didn't have it!
It may be worth taking a look at prepaid options. Depending on your usage, these can save you a lot of money, but there may be the inconvenience of having to pay in advance and handsets are usually not subsidised. However, if you are buying something like the Nexus 5 direct from Google, prepay tariff options are definitely worth looking at!
Another important factor is customer services. This can be difficult to judge: just because a company has won an award, does not mean that it has the same customer services team! Here it may be a case of checking with friends, colleagues and family.
It's at this part of the equation that I'm going to throw in the device choice that you may have. I don't recommend picking a device first, then finding out that the only carrier offering that particular handset doesn't offer you coverage where you work. Fortunately, the situation in 2014 is much better than in 2010 because the popular devices are carried by most carriers, which wasn't always the case.
Finally, depending on your provider you may find that threatening to leave can get you a better deal. If you are going to tell your carrier that you are leaving to try to get a better deal, do check what you can get elsewhere first: don't try to bluff it!