Any aircraft with the requisite equipment will do fine for Instrument training.
I'm a dyed in the wool happy man with my co-owned 182 and could gush on and on about what I like about 182s.
But frankly it's just going to cost you more per hour to burn holes in the sky at 90 knots down an ILS with a hood on flying a 182 vs doing it in something else.
If your goal is the IR, fly whatever is available that'll haul your buns aloft for the cheapest you dare on the "well maintained" to "barely flying" rental fleet.
If your goal is to fly a very nice airplane around and the IR is secondary, buy the 182.
The world looks the same under a hood or Foggles in just about any single-engine bugsmasher cockpit at 90 knots. Unless of course, you have money to burn and like G1000 or other glass panels.
There's also a twinge of "old fart" in me that says "train like you're going to fight". If you're dead certain you'll own a particular type of aircraft outfitted a certain way, or always rent a particular type, fly that or something darn close to it for your training. But cockpits are standard enough (foregoing the above-mentioned glass panel birds) that you're unlikely to meet a panel one day in the clouds that doesn't have all the usual instruments in all the usual places.
One other exception is really old "shotgun" panels with instruments in strange places. If you're going to own or regularly fly one of those in conditions known to attempt to reach up and smite thee out of the sky, do some focused training behind that odd-ball panel.
Nothing wrong at all with buying a 182, but it's wholly unnecessary to step up to a faster, higher load-carrying Cessna before you actually want to go faster, carrying more stuff. That is, of course if you've not yet hit the middle-aged paunch and don't need the additional horsepower to carry your buns aloft, of which I'm borderline.
Me and a well fed CFI in a Skyhawk are going to both need to get comfortable with our sweaty arms touching the whole flight, and leave the tanks less than full at all times. So in my case, I'll put the "bigger airplane" requirement on myself right up front.
But if I weren't already a co-owner, I'd grin and bear the sweaty arm and fuel load calculations to save a few bucks to spend on the airplane of my dreams, later on...
If I were chasing the certificate for a real need. I'm chasing it for fun and challenge so it's hard to get excited about using a pry-bar to wedge myself in and out of an airplane that's going to be near max gross for every takeoff unless I find an instructor who's a twig. Kinda messes up the "dollar to fun" ratio.
