**Core Concept**
Neostigmine and physostigmine are both cholinesterase inhibitors used to increase acetylcholine levels in the synaptic cleft, which is beneficial for treating Myasthenia gravis, a neuromuscular disorder characterized by muscle weakness and fatigue. The choice between these two drugs depends on their pharmacokinetic properties.

**Why the Correct Answer is Right**
Neostigmine is preferred over physostigmine for treating Myasthenia gravis because it is more effective at crossing the blood-brain barrier, which allows it to inhibit cholinesterase in the central nervous system. This is beneficial for patients with Myasthenia gravis, as it can help to alleviate symptoms such as muscle weakness and fatigue. Additionally, neostigmine has a shorter duration of action compared to physostigmine, which makes it easier to manage and control.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not provide a clear reason why neostigmine is preferred over physostigmine. The statement is too vague and does not address the specific pharmacokinetic properties of the two drugs.

**Option B:** This option is incorrect because it is not relevant to the treatment of Myasthenia gravis. While physostigmine may have a longer duration of action, this is not the primary reason why neostigmine is preferred.

**Option C:** This option is incorrect because it is not a direct comparison between neostigmine and physostigmine. The statement is too general and does not address the specific characteristics of the two drugs.

**Clinical Pearl / High-Yield Fact**
When choosing between neostigmine and physostigmine for treating Myasthenia gravis, it's essential to consider the pharmacokinetic properties of each drug, including their ability to cross the blood-brain barrier and their duration of action. Neostigmine's ability to inhibit cholinesterase in the central nervous system makes it a preferred choice for patients with this condition.

**Correct Answer:** D.