The Blackmore WaterALL and Water Tunnel Comparison Chart

Water tunnels were made obsolete years ago by the WaterAll.  You get what you pay for, one reason tunnels are cheaper. At shows attendees have bemoaned the fact that they bought a tunnel after seeing the WaterAll features.  A number of customers have converted tunnels to WaterAlls, just cut the top off and install the waterbars.  No one converts a WaterAll to a tunnel
WaterALL - Positives
Water Tunnel - Negatives
Gentle curtain of water from waterbars won’t displace seed, and bars may be individually and infinitely adjusted to dispense a small or large volume of water on the tray for any application from seeding to sticking to planting plugs, to planting bulbs etc.
High-pressure nozzles disperse seed rather than just watering, yet won’t put enough water out to thoroughly water trays on a planting line.  Nozzles have to be replaced to adjust volume of water, or the belt speed increased or decreased, affecting the rest of the line.
If a few holes in the waterbars are plugged, plenty of water still comes through to get the job done.  As there is no tunnel, but rather an open tub, it is simple to observe what is happening on the tray as it is being watered and if you do need to turn off one bar to unplug holes, there is still plenty of water being put down by the other four bars.
A plugged nozzle reduces the volume of water and nozzles in the tunnel are hard to access to clear or remove for cleaning.  Typically there are not controls on the individual nozzles so the entire machine has to be shut off to work on it, so your line shuts down or goes without water being applied to plants.
No overspray so the working environment stays nice.
Not all the spray is contained by the tunnel so it drifts onto people and other equipment making for an unpleasant environment, wet feet
Very even, directed coverage of the tray with exactly the amount of water you want using simple adjustments on the machine.
Spray goes everywhere, much of the water not even getting on the plants or trays, you waste a lot of water, but still may not get enough on the plants.