Do you know that research has shown that 'staged' properties sell for an average of 10% more $$ and in 50% less time?
So if these figures are true - absolutely worth vacating the property and furnishing it.
However, Rae is right - if it's a lower value property and cashflow is key, then you may be better off keeping the tenants in place.
If it's a mid-high value area, how about a quick reno and a part-staging of the property?
Part-staging is just furnishing a few of the areas - say the lounge, dining area, one bedroom and perhaps outdoor furniture. This is a great way to get the effect of a staged property but without the cost. Many staging companies will charge based on the size of property (2 bedroom, 3 bedroom etc...). Even if you have a 3 bedroom property you can get away with just staging one of the bedrooms. However, if you have spaces that are particularly small (say a small bedroom that you're trying to pass off as a double bedroom), then definately furnish this space. The trick is using small pieces of furniture (eg a small double bed, small side tables and lamps etc...) to make the room look bigger.
A simple but sharp reno can be quick to carry out and inexpensive if you do the right things. And add loads of value (and buyer appeal) to your property. I work with clients all the time advising what and how to renoavte their property for the biggest profit.
You could keep the tenants in place while you reno the exterior and garden and then when they move, get started on the interior. A good way to minimise the downtime on the property.
Plan the reno or anything you're going to do before the tenant moves out. It usually takes a bit of time to arrange trades-people/products etc... so give yourself the lead-time while they're still paying you rent.
Good luck!