Hi Wildcardinside
Of the two in my opinion Lyon would be the better choice.
Paris is great to visit, but talking from experience, it's not the best place to live. The weather is grim, winter is cold, wet and grey, summer warmer, wet and grey. Last year summer began and ended in April The weather in Lyon is much drier and warmer. It also offers the chance to ski in the winter months, the nearest slopes being less than an hour away.
The cost of living in Paris is also huge. Last week I went for a pizza in Paris and it cost 14 euros!!! A few nights later I was in Italy and a similar pizza cost less than 6 euros, and was served by a waiter who actually understood the concept of customer service. While alcohol in supermarkets is quite cheap, drinking out is unbelievable, a beer at the hotel near CDG airport is 9 euros !!! The bars regularly charge at least 7 !!
You also say you don't like too much concrete, the French love the stuff, as you will notice when you arrive in Paris CDG, it is the largest piece of concrete I have ever seen. The geography of the Paris area is as flat as a billiard table with very little to see, Lyon has far more to offer in this area.
Finally nightlife. As a 22 year old I guess it is important to you, I know it was to me when I was your age. Be warned, France is not renowned for it's vibrant nightlife. The majority of the towns and villages in the country effectively close around 6pm and you won't see a soul. Most of the tourist places have a nightlife that rises and falls with the tourist season. That said Paris and Lyon do offer the best of what is avaialable. If nightlife is really important you might want to consider Spain.
Good luck whatever you decide.
Oakbri has a good point, in that France is not renowned for its nightlife and the culture of clubbing in virtually non existent, other than in certain areas like St Tropez in the season. Not sure the reason why, it could be cultural, or that young French people just do not have the level of income to afford it.
I have sons a little younger than you and they show no inclination to visit France anymore on holiday for this very reason.
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