I guess it would depend on what you are going to use it for.The helios is kinda a one trick pony it has a great sound like a modded plexi and can clean up with volume but thats about it.A set it and forget it type.The shiva has an unbelievable clean (rivals my two rock custom sig) and has enough gain to go head to head with alot of high gain amps. I am speaking of the el34version with reverb,i have not played the kt88 version so i can't say on that but i have heard good things about it.Now dont get me wrong i am going to get a helios when i can find one but if you are asking which one should you get it depends on what you are going to do with it,if you want a do all then shiva and if you want to wait 6 months to a year then helios.