As they've now arrived in the UK, I've just ordered some GU energy gels for inclusion in my comparative test. Whilst I was browsing their website I came across a comparison of their own. It reads:
Lining up every imaginable energy gel and scrutinising the nutritional fine print isn't unheard of for serious endurance athletes. The table below provides a quick comparison of the critical components of the energy gels most readily available.
The table is obviously designed to favour their gels. For example, it seems to show that only GU has caffeine and anti-oxydant. Whilst they are not lying strictly speaking, they are really borderline. For example, the SiS Go, High5 and PowerBar have variations that include caffeine. They might not be sold under the exact same name (SiS Smart1, High5 Plus, PowerGel), but they do exist. They've simply not been considered as "most readily available". And I won't even mention the large number of gels on the market that are not even listed here. Furthermore, the choice of "critical components" is totally arbitrary.

What is really missing now is a proper scientific study that would compare most gels in a real race scenario. I guess that would mean involving a cohort of runners/cyclists in a number of races and draw statistical conclusions. I guess that there isn't a single gel that would be perfect for all in all occasions. For example, the sodium intake should be related to body fluid loss which itself is linked to temperature.

Test results in a few days hopefully. Given that a lot of runners (such as Mike M) only swear by them, I'm impatient to taste them.

Ultra biased