Are there differences between buck and flyback?

On paper its the 1:N term... In practice the differences are massive because of snubbers, control, isolation, etc....

Do the basic math on both. You'll see advantages on both sides of the design on paper which aren't too many, but as other people have stated here... You need to define your spec a little better so that we can help because they are two very different switchers which solve two very different problems.

1. Do you need isolation between the AC line and ground (and how much)? (this question alone decides for you if you need a flyback...)

2. What is your efficiency requirement?
Because of the isolation and other issues, most likely the buck will be more efficient.

3. Will you need to meet any FCC or EN spec on conducted or radiated emissions?
Fly backs can be noisier depending on switching frequency, at your power level it may not be to be a that large of an issue... until you fail, then your screwed...

4. What is your cost requirement?
The buck will cost significantly less... no need for an isolated transformer, cheaper fets/igbt because you won't need an 800V part (and with 230Vac in you will need an 800V part, EMI parts will most likely cost less, etc... If you need an opto-isolator (tighter control of output voltages), that will cost you more too.

5. Where is this switcher going or what's the purpose? (powering a digital circuit or gate drive for a bigger design) This more relate to: What's the output ripple requirement (voltage and current)? What are your load transients that you need to meet? Define this and it will help choose.

6. Do you really need a fresh design?
I hate to mention an off the shelf component versus doing your own design. But designing and building a switcher costs development time (easily a month or two if your laying out a board as well). It's a lot easier to build a footprint for a part that meets your needs (assuming it meets your cost requirements) vs. doing a whole new fresh design. Just getting through EMI/EMC testing alone on a production design will set you back a fair amount of lab time plus and time to fix and clear up things to meet requirements versus buying something like this: VSK-S15-48U ($20 in quantity on digikey and probably meets all your requirements including all the EMI/EMC requirements which is not trivial).