It really depends on all kinds of things, like your views and wishes, and there are pros and cons. I can't think of any cons to getting a hamster from a breeder really, other than finding one that has hamsters available at the right time and is close enough to you!
Some people prefer the idea of adopting a hamster from Pets at home, rather than leave it there if it's been there a while. I think for an inexperienced hamster owner though, this might not be the best start as occasionally you hear of people whose hamsters have had an illness and died quite quickly either due to contracting something before being bought, or just bad breeding.
With a breeder hamster you'll be getting a hamster whose breeding and genetics is known and who is used to being handled from birth.
Other alternatives are - rescuing or adopting a more mature hamster either through someone advertising it for sale because they no longer want it, or from the RSPCA (I'll add the link so you can search in your area for hamsters up for adoption if you want).
Or buying a hamster from a smaller more local pet shop. Our hamster is a pet shop hamster, from our small pet shop where we live. They're not perfect but they do look after them quite well and the animals are healthy. I don't think he had ever been handled though and took a long time to tame.
I think it would be nice, as a fairly new owner - to have a hamster from babyhood, bring it up, watch it grow and learn about them along the way. And a hamster from a breeder would be a nice option, but equally a hamster from a local petstore could be fine too, if it seems like a nice pet store.
We live out in the sticks and I didn't even know what Pets at Home was till I came on this forum lol! But I don't think I'd want to buy a pet there personally.
When you've had a hamster or two you might feel you'd rather adopt or rescue an older hamster and give it a home, but it's a real learning curve having them from babyhood and watching them develop
As for species. I've only had a Syrian. They are generally considered easier for a new owner, and more handleable - but that is just a generalisation. As there are dwarf hamster owners on here who have tame hamsters and interact with them. Generally though, dwarf hamsters are smaller and zippier and less easy to handle. Roborovski's particularly. Russian dwarfs vary depending on the temperament.
Other things to think about are Syrians are not generally prone to disease or diabetes so can be easier for a new hamster owner in that respect (although females can get pyometra). All species need a good sized cage - just because dwarf hamsters are smaller doesn't mean they need less space - but the set up would be different. Syrian houses, wheels and toys need to be much larger. Dwarf hamster accessories are smaller and you can fit more of them in, but neither of those things are an issue really as long as the cage is big enough.
It can help to know which species you are getting before choosing the cage sometimes, although Zooplus cages like the Barney and Alexander have narrow 7mm bar spacing so are good for both Syrians and dwarf hamsters, but sometimes a lower cage is better for a dwarf hamster as it's less of a fiddle to set up to avoid fall risks.
All hamsters can get injured and break bones if they fall more than 30cm onto something hard, so setting up a cage to avoid that is important.
The choice was easy for me! I didn't know much about hamsters, we went to the local pet shop and they only had Syrians
and that to me was a hamster. Although we did wonder if he was half guinea pig for a while as he grew huge lol!
I have only seen someone else's dwarf hamsters and they seemed so teeny tiny that I think I'd be anxious handling them! I'm sure you get used to it.
The only other thing I can think of - I'm sure others will chip in with their views - is dwarf hamsters can be awake during the day a little bit sometimes, whereas Syrians tend to sleep all day and wake in the evening.