First and foremost a good food for ultrarunning needs to have some carbohydrates in it. My Go gel has 87kcal in a 60ml serving, all of which come from carbohydrates - maltodextrin to be exact, which I understand to be a form of glucose - but save from a few flavourings, colouring and thickener, that's pretty much it, no salt, no protein, no fat. It is reckoned that you can digest about 200kcal to 250kcal per hour while running, so that would mean having at least two gels per hour. SIS Go gels claim to be isotonic so I expect there are more punchy gels out there.
A 250ml carton of Alpro chocolate soya milk has 175kcal in it - about 40kcals comes from unsaturated fat, 35kcal comes from protein, and 100kcal comes from carbohydrates (sucrose and dextrose a.k.a. glucose). Some studies suggest that if doing endurance sports for many hours then taking in around 10% to 15% of calories as protein can help to minimise muscle damage. The same studies suggest soya protein is the best option as it is easy to digest. Each carton also contains 0.4g of salt and some B vitamins. Personally, I think a mixture of calorie sources rather than just "clean" carbohydrates is better for a long slow burn, and should help to smooth out the energy peaks and troughs I used to experience on long runs (certainly I didn't experience them on the Fling). Plus I like having a steady intake of a little bit of salt.
So I think gels are optimised to deliver energy in short sharp bursts, whereas by some happy accident Alpro soya chocolate milk is good for the longer slower stuff. I reckon when it comes to ultras, gels get 7 points and Alpro gets 8.
2. Taste and ease
Gels are easy to take - tear the top off, squeeze it in your mouth, then neck some water to wash it down. I'm yet to taste one that couldn't be described as nasty though. I think gels are pretty easy to digest - I've never managed more than two on a run but that's more to do with taste rather than not being able to stomach them. The Alpro cartons come with a straw attached and they are easy to drink on the hoof. It is true they don't taste as nice as an ice cold chocolate milkshake made with ice-cream, but they aren't bad - more like a choc-malt shake than chocolate. They are much nicer than gels - it's not even close. I find the Alpro milk very easy to digest - on the Fling I drank nearly 2 litres of it. There is even a strawberry flavoured option for the metrosexuals. The Alpro cartons are UHT so there is no need to calculate defrosting rates and such like to ensure you can drink them as and when required. Gels 4 points, Alpro 7.
There are a few times when I have felt totally empty with no energy in my legs whatsoever, and then ten minutes after taking a gel I feel like I can bound up mountains. So gels work, and the work quick, but that feeling generally wears off after twenty minutes or so. On the Fling, there were a couple of times where I started to feel a bit low on energy (but there were no sudden crashes) so I would have a carton of Alpro and soon enough I could feel my energy levels starting to pick up. The effect was slower but I think lasted much longer. I think it's pretty much evens on this one - I'm going to rely on Alpro for the bulk of my energy needs, but will always carry a gel or two in reserve for emergencies. 8 points for gels, 7 points for Alpro.
4. Value for money
This is perhaps the most important consideration for Scots and Yorkshireman. Gels are pretty much a pound a piece. At two an hour for the WHW race that starts to get pricey. I can get three 250ml cartons of Alpro at Tesco for 85p, and since they're bigger I reckon I only need one per hour. So the soya chocolate milk works out at less than a sixth of the cost of gels. Gels 3 points, Alpro 9.
So there you have my not particularly objective assessment of what is better - chocolate soya milk scores 31 points, gels get 22. I'm sure chocolate soya milk isn't perfect for everyone, and it does have some side effects (an almost uncontrollable desire to stop and hug a tree, or to wear flowers in your hair while running), but it works for me and I think if you're struggling to find the right ultra fuel for you, then it is worth giving chocolate soya milk a try.