The 'barrel' is a better fermenter for wine than the bucket as the lid has a hole for a bung and air-lock (always assuming you don't let it run dry, oops, raspberry vinegar anyone?) which prevents the must being open to the air after the yeast is pitched. Any residual air is quickly purged by the CO2 given off by fermentation. True, a loosely fitted lid will keep the air out for the most part and a vigorous beer fermenting away copes well with draughts and any changes in room temperature. Wine often takes longer to ferment than beer as there's more sugar to digest and the increasing toxicity of the alcohol in the mix takes its toll on the productivity of the yeast, so the added protection of the air-lock protects your 'investment' in the wine a little better. Chances are there's more than £5's worth of sugar and other ingredients (even if they're foraged there's a lot of effort involved) going into 25 litres of wine must so not having the first one ruin pays for the extra cost of the fermenter.
The kit looks fine for the money, although a longer siphon tube would make for faster bottling when the time comes as you can make the levels significantly different.