Fastlane is built in to a pool while SwimEx's Stream is somewhat portable. Fastlane should be installed when the pool is built.

The Stream by SwimEx is going to eat battery power. The amount of current it uses from it's battery or batteries is going to be significant. Water takes a lot of energy to move. It will drain a battery fairly quickly providing enough power to the motor. Typically, deep cycle, marine batteries, such as those used for trolling motors are used and not the kind a car uses for starting. There is a cost premium here.

That Stream is a self contained system that can be rolled to a pool's edge for use or rolled back towards a power plug does make it attractive for existing pools. I think that that is the market they are targeting.

While they show an above ground pool install, there are very few that are safely configured as shown. I would expect to see more in-ground pools with plenty of decking available.

Fastlane, being built in, will run on supplied household power. I would expect a more powerful and longer lasting current being available. It is a separate system from the filter system.

Scott

SwimEX's Stream seems to run on 2 G31 AGM batteries.
The batteries cost around $300 and last for about 800 cycles if used properly. They seem to work for about 1 ~ 1.5 hours of use per charge, if 50% drainage of batteries is maintained for prolonging the battery life. Which means that if I use it every day for 30 minutes, the batteries should last about 4~5 years. Not so bad. The fact that no installation is necessary is attractive, too. Stream is a bit cheaper,too. ($5900 as opposed to $6900 for Fastlane)
As you mentioned, a question is how effective the current is.