The iPhone 5s vs. the iPhone 6 Plus. (Screenshot from Apple's iPhone 6 product page by Hayley Tsukayama)

So you want to get a new iPhone. Well, today's the day to do it: pre-orders started Friday morning at Apple's  Web site and carrier Web sites, though supplies are going fast. This time around, Apple's given you two new iPhone options to chose between: the iPhone 6, with a 4.7-inch screen, or the iPhone 6 Plus, with a whopping 5.5-inch screen. Here are four reasons you might consider that big, big screen -- and getting a new wardrobe with bigger pockets along with it -- plus, a few caveats.

It's great for watching video. One major driver of the trend toward big screens is the crazy amount of video that people are watching on their cellphones. And while Apple's current 4-inch screen will do for a 3-5 minute YouTube clip, it gets a little trying to look at for a full feature-length film. For Apple fans who love video, the iPhone 6 Plus is a very attractive option, and may even be able to replace your need to buy a tablet for enjoying videos on the go.

That said, even at 5.5 inches, the iPhone 6 Plus is not exactly sharing size. You'll still have to get pretty cozy with your friends to watch anything together for a long period of time.

The iPhone 6 Plus will take better video. The iPhone 6 Plus will also come with better video stabilization, which Apple showed off with smooth video of a bumpy mountain bike ride. Steadier video while shooting will be great for parents and more active users, whose families may be seasick from looking at all their shaky footage.

Of course, you still shouldn't necessarily take your iPhone out with you to shoot rough and tumble video; the new iPhones have "ion-strengthened" glass that's more durable than years past, but that doesn't mean it's an action phone.

Web browsing will be roomy. All that space means that you have a lot of room for the mobile Web, so that you can get through more of an article with fewer scrolls. And even though the phone is big, Apple's built in a feature called "Reachability" to let you use the phone one-handed and type in the top of a browser window. Double-tap the home button, and the whole display will drop halfway down the phone to let you reach the top with ease.

Just don't double-click the home button -- that will call up the normal menu that lets you see how many apps you have open.

Fewer clumsy thumb typos. You may have to always type two-handed -- er, thumbed -- but those with clumsy thumbs will also appreciate the extra room to save themselves from some typos. Additionally, Apple's going to update its keyboard software with iOS 8 so that you can use other types of keyboards and will also have better predictive typing options.

Holding the phone might be a bit more of a challenge, but once you get that down you may actually be able to type a coherent e-mail.

The battery life will be good. At least, that's the promise. A bigger phone means a bigger battery, and Apple promises that the iPhone 6 Plus will have a lot of juice.

Screengrab from Apple's iPhone 6 product page. (Hayley Tsukayama)

Don't get me wrong: 5.5 inches is really big, and it's certainly not a size for anyone. But if any of those features sound like must-haves to you, then it could be time to go shopping for cargo pants.