I have had a Grizzly 8" parallelogram jointer w/ spiral cutterhead for about 10 years now. I'm just a hobby woodworker, and even that hobby is part-time with several others. But, I think Grizzly makes a great machine - I also have their 15" planer w/ spiral head, too.
I would NEVER mess with old-school knives again...my buddy had a Jet 6" with blades that were just a nuisance. If you don't mind tinkering with things, don't fear the old blades. If you'd rather spend time being a wood worker, spend the extra for the spiral cutter head.
And by all means, try to get an 8 inch. I had the same dilemma and took the efforts to get a 220 volt outlet wired up. WELL WORTH IT in the long run.
I think the length of jointer bed is going to depend on what type of projects you're working on. Mine are not extra long...I forget the model off the top of my head...either way, I'd vote for a 8" wide, standard length and a spiral head.