Helvetica can be expensive and if you don't have it installed on your PC then, for you, Arial will probably suffice. But just look at the way the glyph's finish on these a's.
Oooh, isn't that lovely? They didn't make a film about Arial did they?
Although desktop printers don't use the same sort of screen as a Heidelberg they don't print solid colour. Only a screen print can do that. Deskdrop printers still measure in a dpi system but it's a little different. Macus will elaborate.
And lastly, seeing as you've opened Pandora's box, all those in favour of Helvetica say "aye" below.