Separate pedals for each effect is my vote. There are pedals that do both fairly well, but it becomes big money to find one that does both [b][i]great[/i][/b].
[b]The Fulltone Choralflange[/b] is one of my favorites. It sounds absolutely fantastic, but you do need to bend down and throw a toggle switch depending on if you want chorus or flanger (They have been in the works for years now on a new model that will be a true stereo chorus, flanger, vibrato)
[b]The Jack Deville Mod Zero[/b] is also a very nice pedal but be CAREFUL on higher regen settings as there is a territory that will absolutely destroy speakers with the spike it has. For this reason, it's not on my pedalboard but it was a contender.
Some of my favorite standalone flangers are the old school DOD bass stereo flanger (prefer that much more than boss) but in the more boutique range I love the Hartman Flanger, and the brand new Stonefish Chorus/vibrato from Greenhouse Effects.
I LOVE the [b]GNI Phaser/Flanger [/b]but that is well over $300 US. I needed it to fit on a small board, and it's the only pedal I've found that had both of those effects in one box, can be used alone or together, and sounds FANTASTIC.