Judging by the number of clicks, the two most popular shares on The Twelfth Magpie these days are Rolls-Royce (LSE: RR.) and SpaceX (NASDAQ: SPCX). In the former case, I imagine being a beloved FTSE 100 big-hitter that’s at the forefront of aerospace and nuclear technologies and up 20 times in the last five years has something to do with it. In the latter, the largest IPO of all time for a company promising to revolutionise space travel might enter the equation.

But which of the two uber-popular stocks should I buy? To get the brain cells firing in search of an answer, I sought ChatGPT’s computer-generated ‘wisdom’.

The question

“Should I buy Rolls-Royce shares or SpaceX shares?” I asked.

The answer was customarily indecisive, with ChatGPT starting with: “It depends.”

But the Large Language Model did say it would lean towards Rolls-Royce, highlighting the large amounts of cash flow and the £7bn–£9bn share buyback programme. Other details were sparse and the conclusion was “I’d be reluctant to go all-in at once”. I don’t think I’ll ever get used to AIs using the first person like this.

What it didn’t mention was that those big buybacks are funded by strong growth in every division. This is truly a company firing on all cylinders.

The SpaceX answer was better, in fairness. The investment case centred around Starlink internet satellite, the firm’s current dominance in launching payload to space, along with ‘moonshots’ like building data centres out there. While details were thin on the ground, the general points were this is an exciting stock with huge amounts of risk attached, which is true.

It’s undeniable that SpaceX has a massive lead in the nascent space industry. The bigger question is whether this industry has the kind of potential – and revenue potential – that some of the boldest predictions are claiming.

Of course, the unreliable nature of AI means I would never buy a stock solely on its advice. It’s too hit and miss. But after my own research, I decided to open a position in one of the two stocks and not the one AI had favoured.

What did I buy?

What was my decision? Well, on the Rolls-Royce side, I was fortunate enough to see the opportunity a few years ago. As such, the stake I bought has grown to the largest individual stock in my portfolio. I still think the shares could be worth considering, though a price-to-earnings ratio of 43 is on the expensive side. But with the price still rocketing – up 35% since May – I don’t want to become overexposed.

As for SpaceX, I can’t deny that the valuation looks expensive, perhaps even outlandish. But the price dropping 50% and going below the IPO level of $135 seemed like an opportunity to me. I like to have a small part of my portfolio in high-risk, high-reward stocks (some have worked out very well with the tech boom in recent years) and therefore I took the plunge.

Should you invest £5,000 in Rolls-Royce Plc right now?

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And right now, Mark thinks there are 6 standout stocks that investors should consider buying. Want to see if Rolls-Royce Plc made the list?

John Fieldsend owns shares in Rolls-Royce and SpaceX.