LONDON -- Insurer Aviva (LSE: AV.L) is a firm Fool favorite. Several of our writers swear by it. Stephen Bland believes it is seriously undervalued, while Maynard Paton likes its 8% income. Cliff D'Arcy rates it a solid buy.

Gosh, I even like it myself. I've got about 5% of my portfolio in the former Norwich Union, making it my single biggest holding.

Stephen Bland has an insane 65% of his value portfolio in the stock. That's how much he likes it -- all of which is strange, considering how badly it has done lately.

Arriba, Aviva!
Aviva may have leapt 26% since June to 3.22 pounds, but it is still down 15% since March and 60% below its precrisis peak of 7.50 pounds. As with most things these days, you can blame its struggles on the eurozone, where it does 60% of its business.

Those strong headwinds from across the Channel won't deter us, because we still think Aviva is too cheap. One day the skies will clear, the wind will change, and this boat will float. It may take several years, but while we're waiting, we can pocket Aviva's generous 8% yield, the third best in the FTSE 100.

Compare that 8% to the interest rate you're getting on cash, and you will see why we are climbing on board the good ship Aviva.

PRU rings true
My fellow Fools are not fans of insurer Prudential (LSE: PRU.L), but I am. I bought a stake back in October 2010 after chief executive Tidjane Thiam made a hash of his attempt to buy AIA Group, the Asian arm of American International Group, and triggered a shareholder revolt.

I like to buy on bad news, and I picked Prudential up at a nice discount. I thought the insurer looked a better deal when it ultimately didn't pay an imprudent $35.5 billion to break into Asia.

So far, I've been proven right. My stake is up more than 30%.

A little divvy
I was naturally delighted to see Prudential deliver a strong set of half-year results, posting a 13% rise in pre-tax profit during the first six months of this year. Operating profit also jumped 13%.

And despite the AIA shambles, it is expanding in Asia. The region may only account for 409 million pounds of its 1.16 billion pounds in operating profit, but it was up 26% over 12 months.

Prudential also raised its interim dividend by 5.7% to 8.4 pence, making it only a so-so income stock, currently yielding 3.1%.

Its share price fell slightly on the news, largely due to profit-taking. It is up 31% over the last 12 months, versus a 17% rise on the FTSE 100.

History holds
Prudential's management warned that the insurer isn't immune to "challenging and economic conditions," and its Asian business has seen some slippage, notably in Korea, India, and China.

It is also concerned about European Solvency II regulations, which could force it to hold billions of pounds in capital to cover its U.S. life insurance business, Jackson. Some feared Prudential might quit London in a huff, but Thiam recently has just confirmed that it remains attached to its "historic home."

My double life
I can see why my Foolish friends have a hotter fever for Aviva. Prudential isn't a candidate for a major rerating. It now trades on a modest forecast price-to-earnings ratio of 12, while Aviva is on a forecast P/E of just 6.4.

These two big U.K.-listed insurers are very different stocks. Prudential looks solid but unspectacular. Aviva is riskier, but potentially rewarding. They balance each other nicely. I'm more than happy to hold both of them.

Your decision may say a lot about you as an investor. Do you want to live the Prudential life or la vida Aviva? Perhaps, like me, you want a bit of both.

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