Thanks for your advice. The specific models I'm thinking about are:
Mid 2015 15.4inch MacBook Pro, 2.2ghz quad core i7 boost to 3.4ghz, 16gb 1600mhz DDR3L, 256GB flash storage, Intel Iris Pro Graphics.
Mid 2017 13.3inch MacBook Pro touchbar, 3.1ghz dual core 7th generation i5 boost to 3.5ghz, 16gb 2133mhz LPDDR3, Intel Iris Plus Graphics 650, 250gb SSD storage.
I'd be editing XAVCS UHD4K footage from a Sony A6500 - hopefully in native UHD4K, otherwise via a proxy before reattaching. Preferably in Premiere Pro, though I have FCPX too.
The videos I'll be making will be under 10mins long, with simple colour grade (possibly with LUTs), basic animated titles and a few cross dissolves / fades. No heavy VFX. Exporting as 1080p for web.
I'd prefer a smaller laptop for travel, reconnecting via Target Display Mode to my late 2009 27inch iMac as a larger monitor. The idea being the laptop will perform better / faster than this 16gb, 2.8ghz boost to 3.46ghz iMac.
Happy to buy a USB-C to everything else adapter to take with, if it means I can travel with a lighter smaller laptop. But really after ability to handle UHD4K straight from camera if possible.
So... with all that in mind.... which of those two MacBooks would be best for me? Would there be significant difference in playback performance and render / export times?
And are either of them actually better than my beefy but old late 2009 iMac?
Many thanks again! Really appreciate it.