The plus means better
I've seen the original Optimus Nova Stove in action, and I will say that the new flame adjustment system on the Plus model is MUCH better. Definitely worth paying the little bit of extra cash. I generally use straight up white gas and can boil 1L of water in about 3min. Coldest I've been is about 10deg Fahrenheit and still was able to boil in the same amount of time. I would recommend buying the cook set as the pot features a coil system on the bottom that is designed to trap more heat than a regular pot - makes boiling a lot faster. I decided to go with Optimus cause I felt like it was much more durable than other brands on the market - I know multiple people that own Optimus and have had their stoves for countless years and they hold up to a beating.
As far as amount of fuel to amount of cooking, my experience is that the 1L bottle can cook for 2-3 people for 5days. Depends on how wise you are about use, what you are cooking, how much coffee you make, etc., but definitely has multi-person multi-day capacity. And I personally don't find the added weight of a little extra gas on the onsite of a hike to be all that cumbersome. Cleans easily, looks great. Can't write enough praise for it. GREAT STOVE!