Seppi 2.66, Simon 1.58
Simon leads their previous meetings 6-1. The last time they met was in August 2015 in Canada. Simon won in straight sets on a hard court. They have only played once indoors though that was on carpet which acts a bit more like grass than a hard court. That was back in 2008 and Simon won in 3 sets.
Seppi has better overall results this year though both have been poor. Simon has won just 38% of his matches in 2017. He has a strong record in this tournament. He reached the semi finals last year and the final in his previous 3 visits. He won the title in 2013 and 2010.
Seppi started the year well with a fourth round finish at the Australian Open where he beat Nick Kyrgios in 5 sets. Since then his best results were probably on grass and he performed well in the short grass season.
I favour Simon to win as he obviously likes the conditions at this venue. He will also have the crowd behind him though that doesn’t always seem to be a good thing for the French players. Neither player tends to do things the easy way. Decent chance of 3 sets. Back Simon if he gets broken.