I don't know about the Inmes model you mentioned, but the Fletcher 5600 is a durable machine for general purposes, especially if you plan to join lots of similar mouldings after one setup. Having one vertical clamp (like most other underpinners) you would have to readjust the clamps for some wide mouldings. For corners with multiple fastener insertions, you have to move the moulding as the driver mechanism is stationary. Cassese machines are good, too.
Fletcher has a significant advantage in its distribution network. You can buy Fletcher machines, consumables, and parts from any Fletcher distributor. To my knowledge, there are far fewer sources for Inmes machines & parts.
If you have a lot of variety in the frames you join -- wide/narrow, soft/hard/poly/MDF, grain finish/vinyl/paper/gesso/metal leaf -- and if you join an average of more than about 30 per week, then the ROI (investment payback) numbers usually favor the Fletcher 5700. That machine costs about $1,000 more, but has two vertical clamps, which eliminate re-setups in process, and the driver mechanism moves, while the moulding stays stationary. It also has some pneumatic goodies not typically found on machines in its price class: adjustable descent speed, pneumatic fastener bale, two separate air adjustments for front & upper pressures, manual/automatic switch, and several optional accessories.