Good choice for me.
Look at Marseille last year and them right now and see the difference Bielsa makes. Proper football (movement, verticality, pressing), players in check and focused. He's a charismatic coach and nobody dares to open up about/against him. All the ballerinas in Arsenal will be at attention and committed at 110% to the club and that's what the club needs IMO : some backbone, some hunger, some fury because they are still "boys" () and it's been proven every time Arsenal met a top club. He would do wonders football-wise though without a real bench, the team will run out of fuel by March/April but I reckon it would really nice for em. Wenger did his time and I don't think he can really do more there unfortunately. It's a shame he didn't win the CL in 2006 but he's now nowhere near winning it soon.
On the other hand, looking at Marseille matches also shows the big downside of Bielsa tactics. For example against PSG it was so obvious : First 15/20 minutes of hell where PSG didn't see the ball and was constantly under pressure, 1 on 1 marking, multiple clear chances and intensity through the roof (shyt really looked like a CL quarter). But even before Imbula's red card that sealed the game, the team started to decline and lose momentum and combined to PSG' superior individualities, the fate of the game was 90% sure (PSG win) because Bielsa's tactics demands way more in terms of stamina and investment than the regular coach and it's the same in the long-term : great start of the season then with the time going on, difficulties to hold the standard as high as it was in the beginning and slow but steady decline to the end (happened to Bilbao for example).