Thanks for your replies and advices, guys.
What seems to be coming out of this topic is there's no reliable company, that ensure consistent quality and above all a "clean" power supply (that's actually my biggest concern !).
Of course, my question was not : "is this specific Lenovo better than a Dell ?" This laptop was an example, amonst many other, of what one can find under $1000.
Whatever the brand is, are there some points one MUST check before purchasing a laptop intended to radio / SDR ?