I'm guessing you mean contract hire (ie fixed rental, fixed term, hand back?)
Your main considerations to be cashflow management and opportunity cost.
The key benefit of contract hire is that you can budget costs exactly - particularly if you go fully maintained. You might 'win' or 'lose' against ownership, but that is irrelevant - you have full control of your costs.
Opportunity cost relates to what you could do with the money to make it work harder - in the case that largely relies on the growth plans for the business.
There are also tax considerations which can only be commented on by someone in possession of all the relevant facts about you and your business.
Which is cheapest - the answer is always - it depends...