It depends on what time of day, whether you are on a bike or in a car, maybe to a degree how good you are at filtering and 'pressing on'.
I used to go through the city in both directions about four times a year for a while, whilst my parents lived in Provence.
It can get blocked. Two Saturdays ago, the queue coming northbound into the city from the south was about five miles long. That was mid-afternoon. There was no queue of any significance coming from the north, though there was a delay of about an hour about 10 miles southbound well past the city, simply due to the volume of traffic heading towards the coast and (of course) to Spain and Italy.
Coming back on Wednesday morning, there was no significant hold up going north (a bit where the traffic divides, just before the first tunnel by when it's too probably too late to cange your mind) and about a mile long queue coming south, starting before the first tunnel in their direction of travel.
In short, you can never really tell.
The trick (if there is one) is to look at the overhead displays above the motorway as you journey along. If it says there is a 'bouchon' (a jam) - or summat similar - up ahead, then there probably is. Coming south, when you get to just before the 'tuning fork' / infinity symbol that (nera enough) marks the point where the motorways have divided, you make your choice, left or right. Stay on the A6 or take the A46.....???
Just a bit before about this point here... make your mind up.....
https://maps.google.co.uk/maps?q=ly...oid=NrMmvJLsr_RN4M1QGsXznQ&cbp=11,172.21,,0,0
Coming north, start to make a choice as you appraoch the Rhone river. Nobody from UKGSer will be with you at that point, so it's down to you.
9 out of 10 times I take the city route... and regret it maybe twice. The outer ring road alternative is OK anyway, so you won't lose too much time if you go that way.