Please next time actually use the scale thread and participate / post there. If we would help each and everyone individually with a variety of requests on different topic each in their own thread the whole forum would be chaos..
Use the Beginners FAQ, the Index and the search engine to find stuff yourself.
FWIW, I dislike the design of the silver one in that second link: I'd rather have a plateau on which a little tray can rest like that black one has.
But I don't know about the qualiy of the mechanisms. I bought a 25$ one from dealextreme that can do 0.001 g next to a 175$ lab scale that can do 0.005 but has a much higher capacity and is super sturdy and reliable. My cheap one is a gem scale, it looks a little bit like the black one you linked to.
That cheap one I have has a casing of very lame material but the mechanism inside seems fine. I don't think I would want to weigh a single DOC dose on it, but weighing a few doses and applying volumetric measurement should be okay. Yes 5-MeO-MiPT and DOX compounds should do okay in solution but as a rule of thumb compounds are less stable in solution, and you need to preserve solutions with something like alcohol.
Most phenethylamines are very stable though, so being in solution couldn't hurt. 5-MeO-MiPT is a tryptamine, but not a 4-HO tryptamine. I'd say try to keep the portion of 5-MeO-MiPT you have in solution to a minimum. For example if you buy a gram, why dissolve all of it right away? Instead first dissolve 100 mg or something until that is used up.
Cheap scales like that might be hit or miss and there is no real way to tell if they are good besides customer reviews and testimonials from the scale thread. How they compare I have no good way of telling, not any better than you can do yourself, just use common sense.
Oh yes and a tip: when you get your scale, it is best not to try and weigh a few mg near zero. If you want to weigh a small amount of something, tare to zero, then put on the tray, then do a little sum in your head to weigh.
Because most of these cheap kinds of balances don't function so well near zero weight.