Syrian (AKA fancy for short hairs and teddy bear for lond hairs)- Largest, Calm, Easy to Handle
Chinese Dwarf- Hyper, Small, Varies in difficulty to Handle
Roborovskii Dwarf- Hyper, Smallest, VERY hard to handle, NOT for beginners
Campbell's Russian Dwarf (AKA Siberian Hamster)- Active, Small, Easy to Handle, Can be nippy
Winter White Russian Dwarf (AKA Siberian Hamster)- Clam, Small Easy to Handle
I posted this to another thread, so I'll just copy and paste.
Hamsters are a lot of work. lol
Cage - Try and get a cage from a good quality brand, such as Habitrail, Imac or Critter Universe. :) Keep in mind with habitrail cages that the tubes are tricky for dwarves to get up as they have no ridged on their feet. If you have a tubey cage make sure the tubes are flat. A tank is a good idea for a cage too.
Food - Once again get a good quality, well known seed mix like Hazel (or Harry in the UK) Hamster, or Ecotrition. Another option is lab blocks, they are healthier, but most hamster don't take to them. Good lab block brands are All Living Things, Mazuri, and Oxbow. Avoid food that have lots of corn, sunflower seeds and fruit as they are just fillers. They always need water. Make sure it is bottled.
Treats - Completely optional.
Fruits + Veg - Feed 2x a week for dwarves. Carrots are great. :)
Bedding - Avoid pine and cedar. Use aspen or paper based beddings. Paper based bedding are softer and look nicer but don't mask the smeel of urine and feces as well as aspen.
Toys - You NEED a wheel. You also need somwhere for them to hide and feel safe. Everything else is optional.
Chews - Make sure your hamster has lots of things to chew on like loofa and wood. :)
Clean Cages 1x a week.
Keeping 2 dwarves together - Dwarves can be kept together, but make sure they are in same-sex groups to avoid babies. Keeping hamsters together is always running the risk of fights, so make sure you have a spare cage incase you need to seperate them. If you are keeping 2 together make sure you have 2 of everything, 2 wheels, 2 hides, 2 food bowls, 2 chews.
They are completely different in personality.
My Syrian was the most cuddly, tame, hamster I have ever seen. His favourite thing to do was to fall asleep in my arms. He was just chilled out.
My Dwarf is very hyper, and much more fun to watch. She is awake in the day much more, poops a lot less. She lets me pick her up and she will sit on my lap and have a back rub.
I like them both for different reasons. Syrians are more inter-active, and draves are much more fun to watch, plus they poop less as they are much smaller. I have heard of dwarves being nippier than Syrians. There are four different kinds of dwarves, the campbells russian (most common, it's what I own), winter white russian (similar to campbells, less common, similar tempermant to syrians), chinese dwarf (very similar to mice), roborovskii (very hyper, and almost impossible to tame). Dwarves can be kept in groups, but expect fights to break out.
You just have to be patient with them and give them their peace ( ie. not bother them every two minutes).