There has been a long-running debate for years about whether it is best to invest in the stock market via a SIPP or an ISA.

Arguments usually come to a head as the deadline for the Stocks and Shares ISA approaches. With less than three weeks left until April 5, many people will be rushing to contribute to their ISA. However, I believe that self-invested personal pensions are often overlooked and deserve a proper hearing. So what will come to the surface?

Given the competing and often confusing tax benefits, I decided to ask ChatGPT to settle the ISA vs. SIPP debate once and for all.

Competitive tax packaging

It started by praising ISAs for their simplicity. The money grows free of income tax and capital gains tax, and withdrawals are completely tax-free. “Investors can get in on the action whenever they want. This flexibility is unbeatable“, said the chatbot.

The biggest advantage of a SIPP was found to be the initial tax relief on contributions. Pay £80 and the government increases it to £100 for basic rate taxpayers. Higher rate taxpayers can claim a further £20 back. It’s an immediate return, and the tax credit generates dividends and growth.

Please note that tax treatment depends on your individual circumstances and may change in the future. This article is for informational purposes only and does not constitute tax advice. Investors should conduct their own research and consider seeking professional advice.

There’s a catch. SIPP money is locked in until at least age 55, and from 2028 until age 57. In addition, withdrawals are subject to tax. ChatGPT declined to announce an outright winner. Quite fair. In my opinion, this is not a basic either/or decision. SIPP and ISA can work great together. SIPPs provide investors with tax relief on entry and ISAs on exit. A balance between the two gives investors the best of both worlds.

Then comes the fun part – choosing what to invest in. At this point I opt out of ChatGPT services. I would never trust him to buy stocks because he is too inconsistent and makes elementary mistakes. Stock picking still requires human intelligence, not artificial diversity.

GSK shares look like good value

One FTSE100 the stock that caught my eye was a pharmaceutical giant GSK (LSE: GSK). The company’s shares struggled for years when former boss Emma Walmsley used the money to rebuild the drug pipeline rather than augment dividends. Investors had to be patient as payouts stagnated and the stock price went nowhere.

Now the picture is improving. Before the recent market volatility, the stock was rising strongly. The GSK share price is still up 35% over the last 12 months, despite a 7.5% decline in the last month. I think this could be a buying opportunity for those who missed out on the recent economic recovery.

The dividend yield is not as high as it used to be. Today it is a more modest 3.3%. However, its price-to-earnings ratio of 11.8 suggests it’s decent value. There is a risk. Drug development is steep, leisurely, and may fail tardy in the process. Competition is also fierce, with rivals racing to bring novel treatments to market.

Still, I think GSK is worth considering long-term. Thanks to recent volatility, I see much more dividend growth opportunities in the FTSE 100 today.