The 4-channel Siglent is 50-100% more expensive.
And with reasons!
-2 ADC (4 channel use 500MSa/s when Rigol do 250MSa/s and full 1GSa/s when two channels in use where Rigol max is 500MSa/s) Even if do not look any other differences this is big difference.
-full acquistion resolution measurements even with 14M length (it means 1ns time resolution with 1ms/div in measurements. (There is also old thread about this)
-Waveform history buffer what Rigol do not have at all. (And with full after capture functions, decode, fft, math, measurements, mask test and also Sinx/linear/dots are fully post processed)
and this is really useful in many cases but because there is not many stand alone scopes with this, there is also lack of knowledge and experience about it. (yes example R&S expensive RTO's have this but of course also higher performance)
-Fast sequence (segmented memory acquistion)
-Sweep frequency analyzing (SFRA aka BodePlot) At this time usable only if you have Siglent external generator)
- Serial decoding "tiny bit better perhaps".
Example I2C two simultaneous independent decoders what both can decode up to 1000 messages (up to 32000 bytes total) at once in one acquistion.
But still, many things depends how user use his equipment and user personal needs.
If need only things what are in Rigol 1kZ then it is also good entry level scope with its price and limits and also technically bit older technology what can see in lack of system processing power. Siglent have LOT of more brute force in system but of course it also use it lot of more. Many hobbyist do not need more than Rigol DS1kZ. But if need, then next higher performance level is Siglent 4 channel SDS1kX-E (and it can also see in price also)