12DT8 vs. 12AT7: Are these two tubes as similar as they appear?

[Lectroid]

When I look at data sheets for these two tubes, they seem to be very similar.  Am I right in that?  If not, what major differences are there.

Has anyone ever used a 12DT8?  I plan to use it in a transformer-less reverb drive circuit.

Thanks!

[sluckey]

One major difference... The 12DT8 can only use 12.6v heater voltage. Show stopper for me.

[HotBluePlates]

When I look at data sheets for these two tubes, they seem to be very similar.  Am I right in that?  ...

Same tube, except for the heater.

One major difference... The 12DT8 can only use 12.6v heater voltage. ...

Use the 6DT8.  Same tube except for heater voltage.  Just like a 12AT7 except for only using Pins 4 and 5 for the heater.

[Lectroid]

Thanks all.  I knew they had to be different, but I completely missed the heater specs.