yes you can own a card from Xapo, and another one from e-coin in the same time; there is no problem about this issue.
But you have to test them and finally i think you will need and use only one card, which have less fees and best quality
The cards from Xapo and E-coin are actually both issued by MyChoice, so the differences should come down to the fees charged and online interface of each company
A big difference seems that with Xapo it works more like a proper debit card, in which your transactions are deducted from your BTC wallet using the exchange rate of that moment. E-coin is more of a pre-paid card, where you have to convert BTC into USD or EUR fund first, then purchases will be deducted from that fiat fund