Airplane vs IFR rating? It all depends. They are two seperate decisons. If
you're sure you're going to fly 150 + hours a year, owning your own airplane
would start to become economic. Less than 100, it almost for sure wouldn't be.

If you're going to have to fly in fairly poor conditions -- say 5 miles in haze
often, or worse -- the rating would be a real comfort. It'd be less expensive
to take the rating in your own airplane, and better for you, since the platform
you're training is is the same one you'll use in real life.

Here's a real life caution: Rated or not, unless you have reason to fly often,
you'll not be proficient. What I had done is to arrange with fellow pilots
(Mooney jocks, we have to stick together) to go as safety pilots for each other
every six months. It changed into a game of trying to get the guy under the
hood really confused before giving him the airplane. You know the drill, 30
degree pitch up, steep bank, a few knots above the stall "It's your airplane".
We became pretty good pilots. IFRers will enjoy this: The safety pilot would
give clearance for a hold, and an estimated time of release. If the pilot under
the hood could make the release time +/- 20 seconds, he won an after flight
beer.

We also, on our home base, flew to touchdown under the hood. That's not as hard
as you might think on a 7000 foot runway in a Mooney because it really tells
you when you're in ground effect. It's a real confidence builder, too. Give it
a try sometimes.