Like others I go up a half size on the Kanadia’s (this is common to all Adidas apparently) and I think they are a better fit for my feet than the 101s. I found the 101s very wide across the toe’s which I also found with the Mizuno Wave Harriers.
The Kanadia’s are a nice compromise as an everyday trainer on firm terrain, they are quite ‘tall’ so roll about on uneven ground but are very forgiving on your feet / ankles.
I found the 101’s very sensitive and similar to running in pumps – minimal ankle support (less so than Inov8 Mudclaws) and they force you to run very lightly over rough terrain. I don’t think the 101 is a particularly durable shoe though – the sole is a bit sketchy on non-muddy surfaces and was wearing down much faster than I’d hoped. I also tore the upper on a hidden piece of metal in the undergrowth – this may have happened with other shoes.
I may buy another pair as you can generally get them for £35 so to that end they’re a bargain, but as I’m trying to limit my number of shoes I’m going to stick with the Kanadia’s for my daily training runs on trails. I also find that the fit of the Kanadia’s is better (closer) so gives more confidence in most situations, I also think they’re grippier. They’d be good for the occassional fell run but I wouldn’t like them on very uneven terrain due to the ‘height’ of the sole.
In summary unless you particularly like a ‘minimal’ style shoe I’d recommend the Kanadia’s for your running and budget. You should be able to find a pair of Kanadia’s for about £40. Also available in garish colours to suit.
However finding a good pair of shoes for me is similar to some peoples experiecnes with tyres – some you’ll love and some you’ll hate.