I don't want to derail this thread further. I don't really understand, which feature is available on the TBS1000C but not SDS1000X-E ?
The TBS1000C has the equivalent of a dual delayed sweep which allows capture and magnification of the waveform *after* the trigger even when it is outside of its record length, which makes up somewhat for its lack of record length. The other DSOs make up for this with long record lengths, but can only show the waveform within the limits of their record length. This means that the short record length of the TBS1000C is not as much of a disadvantage as it otherwise would be.
So for instance the SDS1000X-E has a record length of 8 Msamples, which means at 1 GS/s it can display the wave at up to 3 milliseconds after the trigger. The TBS1000C can do the same thing despite having only 20 Ksamples, and can go much beyond 3 milliseconds.
Both DSOs describe something called "trigger delay" in their documentation, but they are referring to very different things. On the Tektronix (page 72), the trigger delay delays the acquisition like a delayed trigger or delayed sweep would. On the Siglent (page 37), the trigger delay has nothing to do with a delay, and is simply the difference in time between the trigger point and what is shown on the screen. On the Tektronix, this is called magnification.
This is another example of a Chinese oscilloscope company deliberately lying about a feature their DSO lacks.