However, it hasn't been a good performer. Since the original buy was revealed, IBM's stock has declined by 19%. That's largely because, in terms of key fundamentals, the company hasn't done well. Revenue has dropped, on a year-over-year basis, for 16 quarters in a row. On the bottom line, 2015's annual net profit figure was its lowest in years.

But IBM is playing a long game, here. Through divestments, it's slimming down into a business that concentrates only on the highest-margin segments. This process is neither quick nor easy given its massive size.

Lately, though, these moves seem to be working; said segments, collectively IBM's "strategic imperatives" -- i.e., cloud analytics and engagement -- saw revenue grow by a very encouraging 17% in constant currency terms on a year-over-year basis in the company's Q1. The performance of the rest of the company was well in the red, meanwhile.

At the moment, strategic imperatives still only comprise around 34% of the company's overall revenue, but their contribution is becoming more significant.

Don't bet against Berkshire

I am more bullish than many on IBM's prospects. It has a very clear strategy for growth that it's obviously executing well. I'm also very encouraged that the company is willing to take a few hits to its fundamentals and stock price in order to transform into a high-growth enterprise.

But it's up against tough, tough competition with Berkshire Hathaway. Buffett's baby is a money-earning machine, and has been for decades. At this point, it's a massive business, yet still it grows. In terms of book value, it's managed a compound annual gain of over 19%, and last year, it trounced the S&P 500 (not for the first time, I should point out).

There's no reason to think Berkshire can't keep the ball rolling. Anchored by its extensive insurance holdings -- which produce tens of billions of dollars in "float," i.e., money from premiums used for investments -- it can afford to be extremely choosy about the assets it buys.

That, combined with Buffett's awesome investing acumen, means a portfolio stuffed with stocks that have performed solidly in the past, and/or have plenty of potential to do so going forward.

The bulk of these companies have been highly profitable (some more consistently than others, admittedly), they tend to generate cash, and they operate efficiently.

At the core, Warren's investing principles are simple. The great thing about Berkshire is that it's well established, and it's not hard to follow. So, the company isn't dependent on the great man's presence; its philosophy and approach will live on after Warren, and will almost certainly continue to deliver those solid returns.

A crown for a king

While I'm a fan of what IBM's been doing, I don't think that as an investment it can match Berkshire Hathaway. The latter is, in my view, the world's king of portfolio investors. And with the great many advantages it has, combined with its so-simple-it's-almost-genius investing philosophy, I don't see that changing anytime soon, if ever.

I like both of these companies, but for me, the better investment of the two is clearly Berkshire Hathaway.

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