Draining from top has no apparent disadvantages. You can remove the plate it's simple to do so but sucking form top is better. No fluid mixes or damages the quality of oil and you get more and precise fluid out of t which can be measured.
I have a suction machine and air compressor at home too and I can vouch that try draining from the drain bolt and then after closing it connect a suction machine it will still suck more oil out of it which would ordinary take hours to drain from the bolt
Plus when you open the drain bolt it's standard practise to replace the washer with a new copper crush washer and not over tighten. These things are easily looked by most oil change shops( don't expect torque wrenches) so suction method is actually the safest and best method.
All Mercedes and BMW cars have these plates and its routine to only suck from top.
You can see a oil change of any Mercedes at Shahnawaz, they only use the suction method.
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