Well depends on how much you've got too spend. Although there isnt a huge difference in cost but you might be a bit tight.
If you want a cheap but a good and reliable marker get a ion.
If you want a bit more expensive marker with a bit more ' umpf ' then get the PMR.
But finally if you would a one of a kind marker get a ion
then you can let your imagination run wild and make it how you want!