Need unbiased follower eh? Can't really compare either of them (Jedi/Shinigami), they're completely different. Main difference being one is alive and the other is dead!
But if you must, Shinigami definitely win in the 'speed' department I'd say, if they are capable of moving fast enough to disappear (wouldn't that be faster then light travel?). However Force Speed lets the force user move at such a pace that the world seems to slow to a crawl, so the difference might not be too great.
Shinigami win on flashy attacks to, I doubt a Jedi could be able to fend off Senbonzsakura for example.
So that's speed and and fancy attacks covered, other then that Shinigami have Kido, which is probably about the equivalent of the Force. Both have defensive and offensive side's, Light and Dark, Bakudo and Hado. A big problem with the Force vs Kido is that users are fairly biased in what school they follow. A Light user will not have much knowledge of Dark abilities and vice versa. I'd also assume that between either Kido or the Force there would be a lot of similar abilities, Lightning Kido/Force for example. However the Jedi have a lot of abilities that work over area's designed to befuddle people or harm them, Force Stealth, Blind, Battle Meditation and so on. I think a true master of the Dark Side would have the one up on a Shinigami (and anyone else!) though in pure destructive power using or Force Consume, which basically drains the life essence of anything including planets, but apparently only one Sith Lord was capable of that I think. Although that depends on if you'd consider ghosts as an essence of life still. Problem with comparing the two is that there is much more know about the Force then Kido,
Force Powers and
Kido.
In a fight though, it would depend who would get the drop on the other I'd say. However getting the drop on a Jedi or Sith would be nearly impossible with their ability to 'see' what is about to happen. And depending on whether the Shinigami is fighting a Jedi or a Sith would greatly affect how the fight could go. A Jedi could presumably bind everything about them from being able to move, or blind them, and strike at their foe that way or even induce their foe to stop attacking them. A Sith could fire of Lightning attacks, bind their opponent or if they were skilled enough just absorb their essence kinda like a Hollow but unlike a Hollow could conceivably do it on a planetary scale, cant easily dodge something that covers the entire battlefield and then some. A Force user could also completely hide their presence, becoming invisible.
I seem to be leaning more towards a Force user in this regard, but I wouldn't dismiss a Shinigami. They have the speed, and depending on their Zanpakto abilities have a large variety of skills. No Jedi I think would be able to keep up with Ichigo. Kenpachi would probably be fodder to a force user particularly a Sith. Byakuya's Bankai would be difficult to overcome if not impossible without liberal use of shields or energy blasts. Aizen would probably still have the one-up, if he can mask a Force users ability to 'listen' to the Force.
Anyway, in the end, with one being dead and the other being alive, I think its not really fair to compare between the two. Both operate under different constraints and physic's. In a fight with swords, a Shinigami would most likely have the one-up. But with the 'magic' it would be a lot closer if not in favor of the Force user and depending on the fight either a Sith or a Jedi could have very different outcomes.
That's a lot more effort then I'd usually put in for a cross universe discussion!