Whether you’re new to the Apple Watch or are looking to upgrade, you’re going to need to make a decision between getting the GPS or GPS + Cellular version. But how big of a difference is there between the two? And is the addition of cellular really worth an extra $100?

What Is GPS + Cellular?

GPS + Cellular is an option when purchasing the Apple Watch Series 10, among other versions, but what does “GPS + Cellular” actually mean? Functionally, there’s not much of a difference between the two types of Apple Watch models. Everything you can do on a GPS + Cellular Apple Watch, you can also do on an Apple Watch without the Cellular—as long as you keep your iPhone close all the time.

A GPS Apple Watch certainly isn’t useless without a connection to an iPhone, but said connection is necessary for certain features. Namely, handling calls or text messages, music streaming, and (perhaps most importantly) contacting emergency services. The addition of cellular allows the Apple Watch more complete functionality without the need to keep it tethered to another device.

Is Cellular Necessary?

If you want to be able to leave your iPhone behind without cutting yourself off from possible contact, choosing GPS + Cellular is pretty much your only option. If you don’t own an iPhone but still want an Apple Watch, you don’t necessarily need to spring for Cellular, but that means no calls or texts (among other things) being handled through your wrist.

The GPS + Cellular model is also required if you’re looking to get an Apple Watch For Your Kids.

If, however, you carry your iPhone around all the time—keeping it close at work and at home—then there really isn’t much reason to shell out for the cellular function. Once you’ve paired the Apple Watch with your iPhone and keep it close, the watch will work just as well as the more expensive option.

Another thing to consider is what you could do with the $100 you can save by opting for the GPS version. Aside from simply saving your money, that cost difference could also be put towards other Apple Watch options, like sizing up from 42 mm to 46 mm (a $30 difference) or choosing a fancier watch band ($49 to $99 more).

It could also pay for your AppleCare+ coverage ($49 for the SE, $79 for Series 10, or $99 for Ultra 2), which would come in handy in the event of accidental damage, servicing, or emergency tech support.

Some Models Have GPS + Cellular as Standard

If you’re thinking of spending more money on your Apple Watch and going for the pricier titanium-body Series 10 (from $699), the larger and more rugged Ultra 2 (from $799), or an Apple Watch Hermés (from $1,249) then you won’t need to make this decision. These models are GPS + Cellular only, but you’ll be able to use them as regular GPS Watch models by ignoring the cellular functionality and setting them up like a regular model.

This means you only have to worry about which to go for if you’re considering buying the cheaper aluminum Apple Watch Series 10 and Apple Watch SE models.

Cellular Connectivity Can Drain Your Battery Quickly

Both Watch models should get the same rated 18-hour usage under similar conditions. Apple rates the GPS + Cellular model at 14 hours of Wi-Fi (connected to an iPhone) and 4 hours over an LTE connection. But don’t assume that you’ll get 14 hours of LTE usage on a GPS + Cellular model.

In short, a GPS + Cellular model is no replacement for an iPhone. On top of requiring an iPhone be paired to use the device, you’ll want to favor the iPhone connection wherever possible. Cellular connectivity is an added benefit, but it’s not to be relied upon.

One thing that can really help preserve Apple Watch battery life is Low Power Mode, which you may want to turn to if you intend on being away from your iPhone for extended periods of time. That, or consider an Apple Watch Ultra 2 instead of the Series 10 if you can handle the added cost and weight.

Check With Your Carrier First

Another important thing to keep in mind is that cellular service also means getting set up with a cellular carrier. At least it does if you want to use those cellular-specific features.

Additionally, not all carriers currently support Cellular on the Apple Watch, and there are two separate LTE and UMTS models (depending on what country you buy the watch in) that will prevent the features from working if you travel to certain regions. So it’s extremely important to check with your carrier before purchasing.

If your carrier does support it, you also have to consider the added cost of maintaining that service. Rates can vary (again, check with your carrier first), but regardless, you’ll be looking at a larger bill at the end of every month to add your Apple Watch to your plan.

That said, it is possible to buy a GPS + Cellular Apple Watch and hold off on setting up the cellular bits until later. Then you can use it like a regular GPS model by keeping your iPhone close in the meantime.

Ultimately, the deciding factor when it comes to whether ot not you need a cellular Apple Watch comes down to how you intend to use it. It’s not really worth the added cost (both for the watch itself and the carrier fees) for someone who keeps their iPhone on or near them at all times.

The best course of action is to weigh your options and expectations, think about available funds, and figure out how much being able to take and make calls and texts without being tethered to an iPhone is worth to you.