Thanks for your response, and apologies for mine, I was meeting with clients.
For VAT purposes, you can claim 100% of the VAT suffered on the purchase, and will account for VAT charged if and when the equipment is sold in the future. (Assuming 100% business use)
For tax purposes, you can either
1) Claim for 100% of the purchase cost, under Annual Investment allowance, but note that this is limited to £25,000 in any one tax year, so if these two purchases were made in the tax year 2012/2013 or after then this is the maximum you can claim under the annual investment allowance regime, and any excess has to be claimed through the general pool of capital allowances (20% can be claimed on the balance)
2) Just put the items in the general pool, and claim 20% for the year they were purchased and each year thereafter
When you come to sell these items, then if you have claimed under the annual investment allowance (so 100% of the value) then any amount you sell it for, you have to add back into your accounts, as a balancing charge.
If however, all or some or the value remains (as you have claimed all or some through the general pool) then you compare this with the value you have at the time of disposal, and if you sell for more, than that value then you have a balancing charge to add into your accounts, but if you sell for less, then you claim the additional capital allowances.
Bought for £15,000 and 100% claimed,(under the annual investment allowance rules) so the value to carry forward is NIL
Sell for £10,000 then this is added into the income as balancing charge (so in essence you pay tax on the £10,000
Bought for £15000 and claimed 20% in the year of purchase - so as £3000 claimed and £12,000 value remains, then if sold for £14,000 the following year, then you add £2000 into the balancing charge, which means you pay tax on the additional £2000
But if instead sold for £10,000 then you claim the difference of £2000 as a capital allowance.
As to what is financially better for you, is dependent of whether you intend to use this equipment for some time, rather than sell it.
If you plan to use this (for as long as they work!) then there is no harm in claiming annual investment allowances, but if you instead to sell a couple of years down the line, then this could hit you hard in the tax bill that arises in the year you sell either item.
But without full access to you accounts for the last year or two, or knowledge of how the business is growing, its impossible to advise one way or another, with any useful indicators, and then there is never certainty in business !