Everyone has their favorite brands and/or controller types. I have two OCZ Vertex 2 drives (SandForce controller) that work perfectly, but some people have issues with these drives. The M4 and C300 are very good drives which use Marvell controllers.
Honestly, any SSD will be noticeably faster than a hard drive. The question is price versus capacity. A 30 GB SSD will be useful as little more than a boot drive, all other programs will still be on your hard drive. A 60 GB SSD gives you some room to put a few of your most used programs on your SSD as well.
My preference is a 120 GB SSD as a boot drive. 120 GB drives are faster than lower capacity drives, and give you plenty of extra room for installing your programs to SSD, while still keeping your data (music, photos, movies, etc.) on a large hard drive. Also, 120 GB drives usually have the best "price per gigabyte" ratio.