I was thinking about turn by turn play with the Magus.
The first thing I think people will try to do with their Magus is find a way to get into position to do a three action combo of Striking Spell -> Cast a Spell -> Strike.
Shooting Star just needs to be in range, Slide Casting gets a bonus Stride and Sustaining Steel needs to work for it, but lets assume they find a way to regularly be in range of a target and free to hit the combo.
Ok so lets assume they stay in range 2 rounds in a row to execute their combo.
Scenario A
Round 1: Striking Spell -> Cast a Spell -> Strike. Strike hits, you do your damage and then you make an attack with your spell of choice. If you use a cantrip spell your damage is lower than a marital succeeding at two attacks but your accuracy with the spell attack varies between comparable and superior. This all assumes you hit on the first attack.
Round 2: Repeat tactics from Round 1.
Scenario B
Round 1: Striking Spell -> Cast a Spell -> Strike. Strike misses. Baring Haste, your turn is over. This is worse than a martial who at least has the option to try another attack or invest in some defensive tactics like raising a shield but has one silver lining, your cantrip is still cast in your weapon.
Round 2: If you are still in range, optimally you should just Strike here, if you hit you have delivered 1 melee strike and 1 cantrips worth of damage, but you still have two actions to play with. I think the optimal play here is to Cast a Spell without using Striking Spell. Any spell with an attack roll will have a -10 MAP penalty but save spells are unaffected, so our ideal cantrip here is electric arc. This way we potentially can deal 1 melee strike and 2 cantrips worth of damage to a single target. This recoups some of the losses for Round 1 and delivers a bumper Round 2
Scenario C
Round 1: Striking Spell -> Cast a Spell -> Strike. Strike misses.
Round 2: Nothing is in range, the most likely turn of events here is Stride, Strike and then find something to do with that third action. It would be nice if Energize Strikes was available on these kind of off turns.
Scenario D
Round 1: Striking Spell -> Cast a Spell -> Strike. Strike misses.
Round 2: Target in range. Strike (miss) Strike again and hit. We again have an orphaned action.
I'm going to check this out in play at Level 1 and Level 11 and see does it actually play like this.
I'm also going to compare it to a hypothetical character just Striking and casting Electric Arc every turn.