But a TB20 cannot be compared with a TB10. They share only the similar looks. The TB20 totally outclasses the TB10, and every C172/182/PA28.
You forgot about the 182 RG, that one can compete with a TB20/21
- great performance - 155kt TAS at FL080-140, ceiling FL200 which gets you above 99% of non-frontal weather
Similar for the 182 RG, the turbo version (TR182) does 177KTAS at FL200, can easily go to FL240 but isn't allowed to (was fully certified for FL240 but then limited to FL200 to not cannibalize 210 sales).
- the most reliable gear on the retract scene
Low wing retractable gears are much simpler in design and easier to stow but I would argue the 182 RG's gear is one of the sturdiest with typical Cessna long steel tubes that can absorb a lot of shock without making the aircraft jump. I do land at grass strips with the RG but tarmac is certainly better.
- good short runway capability for the type (500m tarmac is easy)
Well, that's not exactly great short runway capability. 500m tarmac is good for two takeoffs with a 182 RG. Short field performance is probably the biggest strength of the 182 family.
- normally-aspirated engine, 250HP, makes TBO in most cases
The 182 RG has the same engine as the TB20 but carbureted and rated at 235 HP. The 182 RG was the first Cessna aircraft to feature a Lycoming engine, reason was that they could not fit the retractable nose gear with a Continental engine. The TR182 is turbo normalized and generally makes TBO and beyond. Carbureted is not as nice as fuel injected but in case your fuel distribution system works well (read: even distribution), the disadvantages are minimal. If you're lucky, you can do LOP. Carb icing is not a factor for the TR182 because the turbocharger heats up the intake air. Never seen my carb temp gauge in the danger area.
Advantages of a 182 RG over the TB20/21:
- short field performance
- spacious cabin (family of 4 + mother in law on vacation including stroller)
- useful load (esp. when compared to the turbo charged TB21)
- high wing (great when it rains)
- large prop clearance
- large number of available STCs (esp. when EASA reg)