The Eb tuba can be used as a solo or ensemble instrument.  This is the tuba used on orchestras in the UK and in brass bands worldwide.  The 14 foot Eb tuba will have the agility of an F tuba for the soloist, and fewer quirks than an F tuba due to its slightly longer length.  Less commonly used in the US, the Eb tuba allows a player to have one instrument that can be used for nimble solo playing as well as large ensemble use.  If you want one tuba to do everything, an Eb may fit the bill.