Check the length of the warranty, if it's any good it should be minimum 7 years, if it's less than that then the manufacturer must think it's pony.
Ideal apparently have had problems recently, a manufacturing fault that means they've had to replace parts on boilers sold last year, presumably that's sorted for what they're selling now.
Finally, how big is the price differential, is it worth spending a couple of hundred more for a 10-year warranty and the very best?