Both the Biesemeyer and Unifence are very good rip fences, either one would serve very well.  Either version of the Biesemeyer and the Unifence will allow its tape measure to be used to very accurately set a distance and cut to the indicated dimension every time.  If you cannot do this with the fence you are currently using then you need to get a better fence!

Biesemeyer

1. The pro version is less prone to deflection than the Unifence, the homeshop version seems to be about the same (I haven’t measured this though).

2. When the Biesemeyer is unlocked and slid across the rail, it isn't constrained to be parallel, it will lock down parallel though.  This isn't a big deal unless you are already used to a fence that stays basically parallel.

3. Since the fence section is basically square it is a little easier to build jigs that ride on the fence.

4. Because of its all steel construction, there is basically no wear on the guide tube.

5. The Biesemeyer has replaceable wear surfaces on the left and right face. If the fence were accidentally driven into the blade the damaged face could be replaced. The Unifence extrusion would need to be replaced in the same situation but it would be more expensive.

6. If the fence faces become damaged they can be easily fabricated out of materials in your shop for very little cost.

1. Has a fence section that can be slid back towards the infeed side; this allows it to be used as a stop block for crosscutting operations. This allows the miter gauge to make cutoffs to the right of the blade without fear of the offcut kicking back. This is somewhat handy on a regular saw, on saws equipped with sliding tables it is VERY useful.

2. The fence section can be rotated to present a low section towards the blade. This can give you more control when cutting thin stock. On right tilting saws this feature allows the blade to extend into the plane of the rip fence, this operation would not be a “recommended” practice though. The low height can also be used when trimming laminates to reference off of the substrate; otherwise the reference would be the laminate which may not be straight or safe to use as a reference.

3. The fence section can be adjusted up or down a small amount to give a normal saw-dust relief at the bottom edge or dropped flush to the table to keep laminates from getting under the fence and binding the cut.

4. The Unifence has more adjustments in the T-square head for alignment. This is what makes the Unifence one of the easiest to align, the Biesemeyer is fairly easy as well but not as easy as the Unifence.

5. The Unifence has only one reference face. If a rip needed to be made on the left of the blade the fence extrusion and attachment bolts would need to be removed and replaced to the right side of the T-square head. This can be done in a matter of seconds but the Biesemeyer has two faces and avoids the issue altogether.

6. The Unifence is easy to micro adjust if the proper unlocked tension is used. By using side pressure from the thumb the fence can be moved to accurately position the fence in very small increments. The Biesemeyer could also be micro adjusted but to do it as well I think it would be a two handed operation due to its non-parallel when unlocked issue.

7. The fence can be adjusted so that it has minimal out-of-parallel alignment when unlocked and moved across the saw.

8. The Unifence is one of the easiest fence systems to install.

9. The locking device on the Unisaw is a steel on hard anodized wear surface. If too much pressure is used to lock the fence down accelerated wear will occur on the interior of the rail.

10. The Unifence is a little smaller and lighter, this makes it a little easier to take on and off of the saw when needed.

11. If the Unifence fence section becomes damaged it would be costly to replace, about 30% the cost of an entire system; this is of course a rip-off!