Well, I suppose "better" depends on your perspective and needs. The SDG1000 series has been around longer, but has two independent (or couple-able, phase shiftable) outputs. The SDG800 series uses newer technology borrowed from the SDG5000 series generators (Easypulse), but with a single output. I personally don't expect to use a function generator for distortion measurements, so the higher distortion is acceptable to me (my old analog B&K FG had a THD rating of .5%, so things are much improved, in any case). Level flatness is as good as my Tektronix FG and SG generators, so no complaint there. I guess if you want the low distortion, and output flexibility, with a Siglent, you have to go to the SDG5000 series.