Is there benefit of early initiation of antiplatelet therapy or DVT prophylaxis in patients who present with large MCA infarcts and are being considered for hemicraniectomy?  

Both aspirin and DVT prophylaxis can be started early in patients on hemicraniectomy watch. There is data on increased risk of stroke recurrence in the first 7 days post-stroke and benefits or early initiation of aspirin (even in afib) and decreasing vascular events, especially in the first few week...

It depends on the surgeon you work with. I generally start or hold those medications depending on the surgeon's preference.

Lovenox would only have a brief effect, whereas aspirin would last for 8-10 days. Hence, Lovenox would interfere less with the surgery.