The definite answer to your question would be entirely implementation-dependent. "Uplink port" is nothing but a mere label - there is no consistent definition for what it is exactly. Typically it would be a high-bandwidth port, sometimes just a transceiver-less GBIC / SFP interface for additional media flexibility.
Whether it has less or more buffer space available than the other ports on the switch would be a question to ask the manufacturer. Whether the available buffer space would meet your specific needs, would be your very own task to determine in your lab setup with your set of load.
This being said, switch-side buffering is typically terribly overrated. Buffers are needed to compensate for different port speeds so the host on the faster link would be able to send data to the slower links in bursts which the switch's buffers would equalize. But since the storage controller has lots of buffer space available to himself with flow control mechanisms at different layers of the transmission (Ethernet if you enable it, TCP in any case), the switch buffers technically just would need to be large enough to hold the amount of ([uplink port link speed] * [number of uplink ports] / [slowest link speed]) + 1 frames in order to be able to keep the slower downlinks saturated at all times. With 2 10G uplink ports connected, 1G slowest links and jumbo frames enabled this would amount to just under 200 KB of buffer space. Due to over-engineering and implementation constraints (e.g. a fixed relation of buffer space to input-output port pairs) you would see significantly larger total buffer space declarations in switches' data sheets.