infernomark, the ion is just as easy to fix as the spyder i reckon bar a couple of problems of which the only way to cause would be the owner messing with stuff.
Most the time the problem in the ion is the battery, and if it was to go tits up, and you got it from warped for example, they would sort it out in double quick time for you.
Id say go with the ion, because if you buy a spyder a couple of months down the line you will want to upgrade, and will have wasted cash in the meantime.
If you are really stuck between the two, have a go on them, see which you like to shoot ... but the ion is a much better marker ... no question.
laters - ste.