You might already know the answer to that question, but in case you're still not sure I thought I'd do a little post to help you.
The first thing to know is that there's no right or wrong answer. The choice is totally yours and the answer can depend on a number of factors. I won't lie, this post is more weighed to the pros of having a second photographer, but if you're reading this it's probably because you want some help convincing - I'm right!
Personally, I love having two photographers on the wedding day; partly for selfish reasons (it's nice to have someone to talk to) but mostly because of all the added value you get.
The Morning
I can only ever be in one place at a time, and wedding mornings are CRAZY! You may think you'll have a really relaxed morning on your day, and for you, it might be, but from the supplier angle, it's all going on. There are bridesmaids to get made up and hair done as well as the bride, there are flowers to be delivered, people popping in to wish you luck, and maybe gifts to give out. And that's just one half of the couple.
The other half are trying to find their shoes, working out which suit belongs to whom and buttonholes to work out how to fasten! All of these things are going on whilst you're having fun with your nearest and dearest which of course, as photographers I want to capture as it's part of your day.
So why two photographers? I can, and I will if I need to, run between the two rooms as people are getting ready. It's quite nice seeing how both halves are before the ceremony. But I'm always worried whilst I'm away from one room I'm missing something in the other. What if the flowers are arriving whilst I'm elsewhere? I'm going to miss that reaction shot! What if gifts are given out? For this reason, and if you want full coverage for both halves, it's very beneficial to have a second photographer involved. That way we can take a room each and make sure we don't miss a thing.
The Ceremony
This may be one of the times two photographers isn't so important, but it's still beneficial in some cases. For example, in a larger venue, it can be nice to have a photographer stationed at one end of the ceremony and the other opposite. That way you can look back on your guests' view of the vows and you also have those lovely shots of your guests smiling and cheering as you say "I do".
Of course, there are some cases where the room may be too small to have a photographer standing at each end, or the registrar/vicar may request photographers stay at the back (it happens) and in these cases, two photographers aren't necessarily needed. Having said that, I've been to plenty of weddings where the photographers have both been stationed at the back and they've been able to get completely different angles; maybe by sneaking down the outside or being higher up.
The Canapes
This is probably the best time to have two photographers. Typically this is when your group shots are done and then your photographer whisks you away for a short time. It's so lovely to have photos of your guests enjoying themselves and this time of day is the perfect time for that. The drinks have started flowing, people are seeing friends and family they haven't seen for years and so on. If your photographer is busy getting those group shots or is with you for a while this is the time a second photographer does their thing! All of my couples say they love the candid shots of their guests so this is the prime time for those.
The Speeches
This is my final example of when second photographers are fab to have. Everyone has a reaction to speeches, some tables usually place bets on the length of them as well. As the main photographer, I want to capture those reactions as those are some of the photos that will spark your emotions in years to come. That photo where Aunt Mabel is falling off her chair laughing? That was because of what the best man had said in his speech, you know, that story about that time you all went to races... The bride shedding a tear? Her dad just did the most moving speech. I'm not lying when I say the majority of what's said in the speeches will fade from your memory very fast, but those photos will remind you of the key moments. I honestly can barely remember the speeches from my own wedding (and it was only 8 months ago) but there are photos I have that bring back those moments and emotions. Back to my point though, I've digressed! Your main photographer will move around the room and get as much as they can, but although they would love to be able to they can't look everywhere at the same time. At least if there are two photographers you have that much more of a chance of getting that hilarious photo of Aunt Mabel falling off her chair.
I know that in some cases budget is a big consideration for people. Maybe you really want two photographers but can't afford the extra? Have a chat with your photographer about the second photography only covering part of the day. Maybe they'll be able to arrange something. We're a pretty flexible bunch and our main job is to make sure you guys have the photos you want of the best day of your life!