What also doesn't make sense is that my 1.6L 2012 Nissan Note is cheaper to insure than my 1L 2002 Nissan Micra...granted the note policy is in my wife's name with me as a named driver, but it still only comes to £100 a month with an excess of £300, where as the Micra in my name with only me on the policy is £118 per month and a £500 excess.
Your Micra is likely to be more expensive because you are the main driver on the policy - and it's the main driver's information that determines the overall price. Then any added named drivers can either increase it or reduce it, depending on their details and driving history.
You might find that if you add your wife as a named driver on the Micra, the insurance goes down - that's what happened when I added my parents to my policy - but it does depend on her driving history as well.
Also, if your wife was the policy holder on your Micra, the insurance may well be cheaper and vice versa with the Note (but the policy holder has to be the registered owner of the vehicle),.
It's funny you mention that about older drivers, when I put other drivers (mother in law etc, all over 50) on my policy the insurance actually went up in price!
It's not just about age, it also depends on driving history - if they have any points or fines on their licences, or accidents or claims in recent years, that could increase it. My parents have both held their licences for many years and neither have any points on their licences or recent accidents or claims, so they bring my insurance down (and it's handy to have them on the car because I've been working abroad for the last few months and they're running the car for me).
So that's why I've taken the policy in my own name...this is my first policy so I'll only have 6 month no claims or whatever, but in saying that, I was a named driver for all the previous years in the UK on my wife's policy.
It's probably good to have it in your name, to build up a good insurance history for yourself, but the downside is that you may well have to put up with paying a bit more than you'd like at first.
Having said that though, car insurance quotes and prices can change a lot between companies, so it's worth trying different companies and seeing what range of quotes you can get. When I was renewing my policy last year, I found quotes that ranged from £200 all the way up to £800 for the same car and same named drivers!