I've owned two straight tail 182s and three Maules, so I'm familiar and I'll interject my opinion here. I think highly of each one, but they are very different. In short, if you're happy with the 182 and are considering another nosewheel airplane, especially a 180hp tricycle Maule, keep the 182. I don't think you will gain anything by making that move, other than being able to say your airplane is a '99 model instead of a '57 model.
The straight tail 182 is a super all-around airplane with both great utility and cross country capabilities. You won't see the 130-135 knot cruise in the Maule and you'll miss the extra 50hp on takeoff and climb, especially when hot, high, and/or heavy. I just did a short stint with a 180 hp airplane after being accustomed to big hp. It didn't suit me well. However, if you fly solo or keep it light all the time (or always have plenty of runway) and are looking for better economy, then I suppose you may be happy in the 180hp Maule. But under a load or high performance requirements, it won't compare favorably to the 182. For an airport to airport plane, the 182 will win.
The Maule will handle lighter in the air and will be more fun to maneuver and play around in. The Maule seems to me to shine in more of a utility/off airport/short/rough field airplane. But put a nosewheel on it and you've just taken away a lot of what it was designed to do. So unless you need a conventional gear airplane for your mission, or want a tailwheel just for the fun of it, the 182 is a hell of a lot of airplane for the buck. The nosewheel Maule...seems like a combination of attributes that...well, I don't fully understand. I'm sure the guys that fly them will point out what I'm missing.
This, of course, is only opinion. And for the record, I am a Maule guy. Mine suits me perfectly and I love it. I want a 182 to carry the family cross country. I want a cub/husky for rough/short work that I do regularly. The long wing Maule on 35s is a compromise between the two that works great for me.
If you're itching to spend $70k to upgrade, there are a lot of nice 182s on the market to be had in that price range. On the other hand, if you want to venture into the tailwheel world, the Maule is a fantastic airplane, also available for $70k.