I wanted to buy a spare tube to carry while riding, but it appears there is wide choice: the first website I checked carried 92 items in the tube category, another one had 69, with prices varying from 3,29€ to 16,5€ (that's 5x).
What should I look for aside from size and valve type? Does brand make a difference, or is it more like “grab any one, they're all the same”?
I've heard a few people say brand doesn't matter and they all come from the same factory / country. I've had bad experience with some tubes though (ok I'll mention them, BBB). They would bulge in places.
I've typically had no problems with tubes from the major tyre manufacturers like Michelin, Continental and Schwalbe.
Schwalbe marketing suggests their tubes hold pressure longer than other brands due to higher quality standards or possibly more butyl, and Michelin does too for their butyl tubes. Lightweight or Latex tubes will not hold pressure as long and need to be pumped up more often.
I tend to think the large tire manufacturers know their rubber, they have better quality control and they care about their reputation. So I don't subscribe to the "they're all the same" philosophy.
At my LBS there is little price difference, if any, between say a standard Michelin tube and a BBB. The price difference you're seeing may be for specialist features such as very lightweight, puncture resistant, latex etc.
Unless you're looking for a lightweight or specialty tube (latex, flat resistant, etc), make sure you've got the right size and right type and length of valve stem and you're pretty much good to go with any butyl rubber tube. Most tubes out there are simply re-branded Kenda tubes, anyway.
Schwalbe tubes are both Seamless (they're extruded rather than vulcanized pieces) and have a higher butyl content. The are made in their own facility, and they don't make tubes for anyone else. They've been independently tested to hold air better than anything on the market. So no, not all tubes are the same, they`re not made all in the same facility!
I always use Latex tubes. if you buy any of the huge company like michelin or schwalbe you can be sure to have "good" tubes. but i had 2 flat tyres in 6 months using butyl and i'm now cycling almost 6 months with Latex tubes and i didn't have a flat tyre, you'll need to pump your tubes every-time you go for a spin because latex looses his pressure pretty quick (3-4 days and my tubes have no pressure left)
latex is a bit more expensive than butyl but that's only a couple of dollars. probably cheaper than time you loose to put on a new tube
Tubes with Schrader (auto) valve sometimes have a gum padding around the base. This is intended to reinforce the tube but some MTB rims do not take the wide valve with additional padding around the base. My MTB-style E-bike has Schrader valves but does not this wider standard, for instance. I was reluctant to drill these few mm so the purchase has been a complete loss.
