I have a Miele T1 heat pump dryer. Drying a load in this dryer consumes around half the energy of a vented electric, vented gas or electric condenser dryer.
However gas is typically around one-third the price of electricity. So even though a vented gas dryer does use twice the energy of a heat pump dryer, a gas dryer will still typically work out slightly cheaper. Gas rates tend to be fixed whereas electricity rates can be tiered and also based on time-of-use for some customers in some places.
Electricity in Australia is mostly generated by burning fossil fuels. Although a gas dryer uses twice the energy of a heat pump dryer, this is still thought to be better for the environment as you are still emitting less carbon dioxide by using a gas dryer.
So if you can get a gas dryer, this would be the way forward. I used to have a Maytag Neptune gas dryer and it worked very well and had accurate moisture sensors and could dry quickly at low heat. But it did ball bedding. If you must have electric then I would say a vented would be a better choice than a condenser. This is because they typically dry faster, they don't give out heat to the room, they leave the load cool and dry at the end, they normally use slightly less electricity, they are simpler and can often be quieter and cheaper to buy.
However if you don't have a dryer vent installed and you can't install one for some reason, then I would say a heat pump dryer would be a good choice rather than a traditional condenser. This is because they give out far less heat to the room than a regular condenser and they consume half the energy of a regular condenser but are usually more expensive to buy and can be noisier or sound like a portable air conditioner.