I like an oscilloscope with good performance and with these features:
1) Low noise possible. This is the primary objective. (Probably I need to purchase ather probe becouse the standard probe seem not good).
2) Good precision (in vertical and horizontal).
3) Good trigger.
4) Good quality of imaging (interpolation and anti-aliasing)
5) Good sensibility (minimum 2mV)
For <500$ the Owon SDS7102 is best choice ?
1) not the most low noise possible, not even close
2) forget it, Owon only cares about one thing, low pricing
3) most DSO' s are not bad at that
4) buy a agilent, Hameg or the expensive Rigol line
5) Hameg rules there
But for this budget you have not much choise. All these topics are alike, how to get the less worst scope for as little money as possible. Good scopes cost money. How good you need is up to you. But at 400 dollar it does not matter.
I do not agree totally with Dave about the older Tek DSO's. I had a " pathetic" 60 MHz TDS210 for a while here to play with and it was
for my use (so for what was important for me) a better scope as my former Rigol DS1102E (still find that my biggest waist of money (900 euro back then for the most crappy piece of shit I ever bought, and I really wished I had not read all those good critics about it back then, so that is why I am maybe a bit over-negative, but it was my hard earned money down the drain), but if you are into digital stuff the Rigol probably is better.
and all these Chinese brands are rather close and only interested in lowest price. An Owon and two extra real good probes cost probably more as the Rigol and Rigol probes (RP2200) are also rather bad (response is much worse as a 20 year old 100 MHz Tek and mechanical they are a disaster (I slaughtered one that died after a few months)
just my two cents. (I have now a 350 MHz Hameg DSO (still love it as much as the first day) and a dozen Analog scopes, most from Tek)