You should look at benchmarks of latest iPad Pro vs. Mac laptops. iPad Pro is faster than lower end Mac laptops and only a little bit slower than MacBook Pros.
Only in benchmarks. Look at the workflow presented in article. There is no builds required nor CPU heavy processing. But there is a lot of switching between applications, multi windows etc. iOS UI is not prepared for this kind of workflow. Even the newest improvements on iPad Pro are far away from being as useful and as fast as on normal laptop.
Sorry, I misunderstood you. The way you phrased your earlier comment ("Mac with SSD") made me think you were talking about hardware performance.
On macs with without SSD UX is lagy
Why does graphics performance matter for programming? (Game design excluded of course)