well since you asked
The EHX series of octave pedals in my opinion has a whonky clank to it. like greg said, it's got a sort of organ tone to it, but i'm not sure how usable it would be. i couldnt really get a texture out of it that i liked.
the oc-2 is analog and the oc-3 is digital. they both were the standard for a while, and in all honesty, i really enjoy both of them. That reason being this: if you play a string very hard fingerstyle, it sounds like you had popped the string.. that overdriven punch. the boss pedals have a certain level of separation of their notes so that even while the effect is engaged, you can still capture that texture while you're playing. it's really nice for dynamic playing with an octave pedal. they also have a certain type of growl to them that is stank nasty. Oteil Burbridge comes to mind. i've got some audio files i may be able to post for examples. i still miss it to a degree...some days more than others.
the ebs is a very smooth sounding octave. it tracks pretty well, but the texture isn't rough enough for me. it almost sounds too smooth. One thing about octave pedals, is that it's best to try and hear them played live, or with some air moving. I think all of the manufacturers or the sound files you hear are putting up sound reviews of pedals that are going direct to sound cards.. which is a nice way to hear things, but not really a realistic representation of what it really sounds like. the prunes and custard as well as the octave effects and many others really require some air moving to hear what they sound like, as well as what textures they offer for playing applications. another thing about the EBS is that it has those switches. 2 octaves below is pretty useless in my book, but some people like it. the octave up is a bit gimmicky for me considering there are other options for lead line bass parts.
the MXR is a great alternative in my opinion. it doesnt offer 2 octaves below, since no one uses it anyway, but it provides 2 different octave textures.. the growl of the boss series, and the smooth fatness of the ebs. blending the two makes for some nice flavor as well. it has a mid switch which adds practicality to live applications since your mids do drop out once those subsonic frequencies start rumbling around. I like to boost the dry knob quite a bit, as this octave pedal tracks so good, that it doesnt have that same separation that the boss series has. I just got used to that sound over the years, and when I got my MXR, i sat down for a while and found the setting that provided the same texture as I had my Boss set up. however, it's like 99.5% the same. You can still overdrive the string and get that pop, but the octave effect is stuck on it like glue.. so all in all it's still incredible, and the octave texture has some nut to it. I got great reviews from band mates, as they were like.. "i heard a different kinda rumbling over on your side of the stage tonight, what's up?" kinda thing. so it delivers for sure. Greg swears by the mid switch and keeps his on, but I honestly go back and forth for different applications. Sometimes i want that vacuum bass tone
last on the list is the Aguilar Octamizer. I dont think i like how it sounds based on all of the sound samples and marketing that they've been doing.. And people on here seem to love it, but I just can't get along with the hype. I think i hear a different sound in my head when i think Octave. So i'm glad so many people are happy with what they've found, but that grit is where it's at!
hope that helps, for what it's worth