I am interested in wedding photography. I currently have a 50mm f1.8 lens. I am going to purchase my first full-frame camera soon. I can only afford one lens right now, so I need to decide between body + 24-105 f/4 kit lens or body + 70-200 f/2.8. Which is the best choice ?
So I need to decide between body + kit lense or body + 70-200 f2.8. which is the best choice ?
Of the two, the EF 24-105 f/4L is the better choice, considering that you say you're interested in wedding photography. Presumably, that means that you'll be taking photos of people at close and medium distances, and a 70-200mm lens is just too long for that kind of thing.
However, both a full frame body and either of the lenses that you mention are pretty big investments. Make sure that you have a good understanding of what you're buying and how it'll work for you. Yours is a pretty basic question, which is fine, but it gives the impression that you'd benefit from more research before you start spending your limited funds. For example, it seems strange to limit your range of choices to just two lenses. Many photographers prefer a 24-70mm lens, for example. And you haven't mentioned which full frame body you're looking at; if you're thinking of one of the current 5D models, you might be better served by going with the lower budget 6D (or a used body) and spending more on lenses, lighting, etc. Don't limit your choices before you understand what you need, and don't spend your money before you know what you'll be getting.
Assuming you are looking at new cameras and lenses, you might want to consider buying second-hand and discover that your budget might cover an older full-frame body (say a 5D Mark II), the 24-105mm f/4 general-use lens and a 70-200mm lens (will the f/4 do, or do you need the f/2.8?) with some spare cash for a flash.
Along with the 50mm lens you should have a reasonable but basic kit bag. If you still have an APS-C body then you might want to hang on to that as a second body (with the 70-200mm) so you don't have to swap lenses.
I use an EF 24-105mm f/4 L to take more photos with my main FF camera than probably any other lens. But while it can be a good wedding lens when used with flash, it is not a great wedding lens. The f/4 maximum aperture is a bit too limiting to be your primary wedding lens. For that one of the 24-70mm f/2.8 zooms is better.
If you can't swing the cost of the EF 24-70mm f/2.8 L II, the Tamron SP 24-70mm f/2.8 Di VC is a very good alternative. While not quite as sharp as the new Canon, it is better than the original EF 24-70mm f/2.8 L (and my classic 24-70/2.8 is still very good - it's sharper than my 24-105/4) and it offers Vibration Compensation which is Tamron's version of IS. Sigma has announced a new stabilized 24-70mm f/2.8 ART lens that is supposed to be available in the USA on August 24, 2017. Until it has been in the wild long enough for real world reviews and tests to be done we won't know where it stands in relation to the others, but if it is anything like most of Sigma's recent ART lens releases it will be a great lens. Tamron is also expected to release a G2 (generation 2) version of their 24-70/2.8 in September 2017. The newer version will be compatible with Tamron's Tap In Console, their answer to Sigma's USB Dock that allows end users to update lens firmware and do detailed lens calibration via their own computer.
If you are going to shoot weddings you are pretty much going to need a 70-200mm f/2.8. You might could get by with an EF 135mm f/2 (phenomenal lens - especially for the price) and a good 1.4X extender/teleconverter for your telephoto needs, but by and large the two essential zoom lenses for wedding photography are a 24-70/2.8 (or a 16-35/2.8 + a 50mm prime) and a 70-200/2.8. Some wedding shooters only use fast primes (24, 35, 50, 85, 135, etc.) and that works too, but you will find it difficult to shoot weddings with an f/4 lens as your primary lens.
My advice is to get the best 24-70/2.8 you can afford and go from there.
I love my 24-105/4. It is a rock solid workhorse. It takes a beating and just keeps on going. It gives very good (but not great) image quality. It's performed in the pouring rain, when getting run over on the sidelines at sporting events, when being bled on, and in spite of being dropped on solid concrete. But it is not my first choice when I am shooting a wedding or other event where it is just too dark for f/4 to work. Then it is time for my 24-70/2.8 or my fast primes.