Wyeast Belgian Saison 3724 likes to ferment at 70-95 F, 76-80% attenuative, low floculation--reportedly the Dupont strain
Wyeast French Saison 3711 likes to ferment at 65-77 F, 77-83% attenuative, low floculation--reportedly the Brasserie Thiriez strain
I used both strains--pitched one smack pack (3724) in one 5 gallon carboy and the other smack pack (3711) in the other carboy. Fermented in March at temps around 69-73 F, IIRC. No starter was used.
Belgian took forever to ferment, got stuck around 1.035 after 1.5 weeks, and proceeded glacially thereafter (finished in the single digits after 4-5 weeks. Took forever to clear, as well. However, many say it is the better tasting/smelling one of the two strains. I'd suggest using a starter AND fermenting a little warmer (e.g. 75-78 F) initially, and consider creeping a little warmer (closer to 80+ F) only if needed. However, given that Wyeast says the strain can ferment as high as 95, I wouldn't worry too much about it. It may result in more esters, phenols (desirable), but possibly at the expense of headache-causing fusel alcohols.
The French strain (3711) was a vigorous fermenter, blew the 3-piece airlock and stopper off within 12 hours of pitching! Fermentation was done within 1.5 weeks, and the yeast dropped clear. I think the aromas and flavors are the same. But, not everyone else does, so YMMV.
Some start with Belgian and finish with French Saison yeast.