Typically I rent a car once I know my travel arrangement. Prior to travel/getting there, I will apply a free day code, or $$ off code. Compare the price with their weekend special and eventually will even book through Enterprise. Lately, I've been noticing that Enterprise prices are cheaper than National, and it is the same stock. Is there any disadvantage to book through Enterprise, under Emerald Club log in?

Other than not really having a "real" rewards system? Not really. Been using Enterprise a lot more since it's been cheaper.

If you're renting under Emerald Club login, you're earning the same credits as if you'd rented with National... I'm not sure your point about the lack of "real" rewards?

How do you link Enterprise Plus and National Emerald?

You just login on the Enterprise site using you Emerald Club info ptior to making a booking.

On the Enterprise page, towards the bottom, it gives you the option of LOYALTY PROGRAM, click through it, next page select Emerald Or National, enter your Emerald # and last name, and there you have it. Without using any codes or coupons, their prices are cheaper than National with coupons/codes/$$ off, etc, and it credits back to you.