Some info that might help
. Robos are very fast and notoriously difficult to handle and tame. They are often considered more watching pets but can be funny and entertaining. They also come out during the day sometimes and are out a bit more than other hamsters generally. Although some can be nervy and shy. Their personalities vary and that is the case with all species of hamster. Lifespan is supposed to be 2 to 5 years but average is probably 2 years.
Russian dwarf hamsters will all be hybrids unless you get one from a breeder and know it is a pure bred winter white or Campbell’s. Otherwise it will be a hybrid of these two species even if it looks like one species or the other. They are still lovely pets but are predisposed to diabetes and need a sugar free diet. They can be more prone to a slightly shorter lifespan but not always. Lifespan is generally about 2 years but can be less. They are easier to hand tame than Robos but not always that easy depending on the personality again.
You didn’t mention Syrian hamsters (aka teddy bear hamsters). They are generally thought to be the best for a first time owner and the easiest to tame and handle. Lots of interesting personality quirks. Some are lazy, others maverick!
I would normally suggest a Syrian for a first hamster but if you’re sure you want a dwarf hamster I would go with a Robo- but expect it to be a look don’t touch pet. They are less likely to have health issues but any hamster can become susceptible. We had one that developed a lump at 18 months which turned out to be cancer and lived to just under 2. Had expected him to live longer than our Syrian but it didn’t work out that way. Some of that is down to luck due to uncertain breeding.
Cage wise you would need something at least 80cm x 50cm and not taller than 40 to 45 Cm ideally - for a Syrian and a Robo. Or 70 x 40 minimum for a Russian dwarf.
Lower height cages are best for robos as they can injure themselves if they fall from a height. Ours was in the Savic Mickey 2xl which I found a very good cafe for a Robo especially as it has good front access - easier for interaction- and 7mm bar spacing. Also called the Lixit Mickey 2xl in the US. It is also ok for a Syrian or Russian dwarf hamster although most people would go a little bit larger for a Syrian - mainly because they need bigger items that can fill the cage up - but it’s fine if set up carefully.