260hp is the minimum I would want for IFR due to climb performance. I think the 250hp will have a Bendix pressure carb. These aren't bad, but I suggest you buy the manual and get very acquainted with its repair and tuning. They aren't difficult, and the new parts for them are of a support quality so you will likely only go through it one in a lifetime, but the talent for dealing with them is fading away so it would be good to stockpile the knowledge and an overhaul kit incase either are scarce when you need to do them.
The 225hp has some advantage in that it can be STC'd for Mogas in case leaded AvGas becomes unavailable, but I don't really see that supply disappearing before an unleaded replacement comes to market. There are plenty of STC mods to keep those engines going and even improve them, then there are also plenty of upgrade options to IO-470s, and depending on model 33, even 520 and 550. I'm not sure on the 33, but the 35 even had a 350hp TIO-540 Machen conversion available (my understanding is that these are highly limited in their ability to use this horsepower as they can't get rid of the heat, having seen one in the cowl, I believe it).
What is a bit misstated is the value of the limited panel upgrade in the 225, which IFR GPS? Is it a WAAS unit capable of all the approaches to their minimums? None of this equipment is going to carry your plane into the future. There are those that are kicking and screaming about it, and they will have G airspace and likely have a transponder requirement.
NexGen is coming whether you like it or not, may as well take advantage because we spent ****loads of money orbiting the Space Shuttle to map the planet (most of it anyway) in 3D. To not take advantage of that is truly a waste of tax dollars, it doesn't just have to be the military that utilizes this data.
Best thing to do is evaluate the condition of the airframes first, that is the priority. Airframe repairs are expensive and put your plane out of commission for extended periods, all the while devaluing the plane.
Next evaluate panels. Anything that isn't WAAS has no special value, it is antiquated and only semi functional in the realm where it matters most, approaches to minimums. You want to avoid having to pay for the glass transition unless you want exactly what you want. Luckily I had a buddy CFII who would always get the latest glass during the transition, and I would do an IPC in it. I got a good enough airframe and engine package, it was worth it to me to put in what I did.
The downside to getting to fly the equipment on my once a year IFR flight is I also got to see how this equipment made operating in an IMC/IFR environment once a year considerably safer and simpler to maintain superior situational awareness not only in ease but in accuracy as well. When coming out the bottom, there is little doubt of exactly where the runway will be regardless of how wild the ride down was.
If you are as most IFR pilots, a rare one, then your safety benefit increases the most.
There are ways to have non certified displays in your panel so long as they are not being used as required equipment. Plenty of low cost/high quality stuff in the Exp sector. The loop hole is in how they are held in place. Velcro is your friend.
Depends a lot on how you're going to load it.
There are bookoo NA 182 drivers flying IFR safely.