27‑inch iMac 2017 i5 vs. i7 I own a bit old MacBook Pro (Retina, 15-inch, Mid 2014) with 2,2 GHz Intel Core i7, so I'm considering replacing it with a new iMac, but not sure which CPU should I choose.


3.8GHz quad-core Intel Core i5, Turbo Boost up to 4.2GHz (MNED2LL/A) for € 2,699
4.2GHz quad-core Intel Core i7, Turbo Boost up to 4.5GHz (Z0TR) for €2,939


I'm a software developer who's stack is:


Python
Swift for iOS and macOS development
Docker
PostgreSQL
Javascript


I'm concerned if I benefit from purchasing an iMac with i7 for extra €300. Please advise. Thanks!
Software development tends to be a very CPU-centric task, but the question is whether or not a few extra GHz is going to buy you significant enough longevity to stave off your next computer purchase by any significant amount. I somehow doubt it. I'd go for the 3.8GHz i5.

...or at least I would, but you mentioned Python. Python is one of the slowest of the various interpreted languages commonly used. It can use all the help it can get. If you do a significant amount of Python coding, I'd go for the faster processor.