Under a lease, the leasing company owns the equipment. On the other hand, if a loan is taken out to purchase the equipment, the company will own the equipment once the loan is paid back. Depending on the type of lease, the leased equipment may or may not appear on the company's balance sheet. The choice of lease or loan will depend on the company's tax situation and the criteria imposed by the financial institutions.
From a tax perspective, an operating lease will give rise to periodic payments which will, in principle, be tax deductible. In the case of a financial lease, the asset will no longer appear on the lessor's books but rather on the books of the lessee, resulting in (tax-deductible) depreciation. Thus, both types of leases can generate tax-deductible expenses. However, for timing and financial reasons, one type of lease may be preferred.
Further, please note that certain types of assets may qualify for specific R&D tax incentives (see question "Are there any tax incentives available to R&D companies and, if so, how can I benefit from them?").