any time there is a problem the peace of mind of not having to worry about the costs is worth it IMHO
From GG's above sums, you can put a price of €500 for this peace of mind.
If going the second-hand route, this means finding suitable car, visiting dealers, getting a deal, arranging finance (if needed). Taking a certain amount of risk on a second-hand car in terms of it's history and level of servicing done / maintenance required.
That figure helps look after any unexpected servicing issues (balanced against above, in terms of level of warranty / guarantee available), or general increase in running costs over time.
I've gone car allowance in the past when available to me, but on those 2 occasions I already had a nice car which was fit for purpose, and secondly I was unsure of staying with the job long term, and in my role a company car wasn't always a given if I were to move.
I think motoring at present is a little uncertain, lots of talk of increased carbon taxes which will mean increased costs for the motorist, a tide turning against diesels but people not fully convinced by EV's yet. I'll through Brexit into the mix for second-hand car values, as this has caused issues in the market before.
I would be very tempted by company car for that peace of mind - if the car on offer was suitable, and the job had long term prospects.