Not sure if this relates to the OP's question or not, but the thing I find a little unnerving about the Ideal purple wirenuts, is that the manufacturer has multiple warnings on the package that they are designed only for connecting aluminum-to-aluminum conductors with another copper conductor present, but not for straight aluminum to aluminum only.
Not sure about the T&B Marette ACS wirenut though, but according to the T&B product literature, they are not even UL Listed, so not sure how you could actually use them.
If I need to splice small AWG aluminum to aluminum or aluminum to copper, which thankfully is a rare occurrence for me, I use the AlumiConn set screw type connectors and a torque screwdriver, so as to make it a UL Listed splice. These still can take up a lot of room in a box, but IMO they are presently the next best alternative to the actual Copalum splices
