Some people almost religiously prefer high wing - other's prefer low wing. It doesn't make a lot of difference except that the view of the ground is less restricted with a high wing, and the view into a turn is less restricted with a low wing. Both types require similar sorts of help from the pilot to make them fly.
The Warrior is heavier than the C150 and is more stable. The extra energy to lose before landing requires marginally more planning for the approach in that it's easier to lose excessive enrgy if you get it wrong in a 150 - but having said that a perfectly flown approach in a 150 would look pretty similar to a perfectly flown approach in a Warrior.
The Warrior will float for longer during the flare than a 150 - especially if you approach with excessive speed.
Stalls are a non-event in a Warrior and for cruise flying if you point it in the right direction then it needs much less input that a 150 to keep it in that direction.
Most people that I've converted to the Warrior from a two seater underestimate it's glide performance and so take a few goes to sort out practice force landings, tend to touch down long until they get used to managing the energy in the approach, and tend to want to let it touch down to early, but don't generally have any trouble other than that. It doesn't usually take very long to sort out.
How long you need to convert depends on how quickly you take to it - a couple of hours might be typical but it depends on all sorts of things.