The access tiers available for blob storage accounts are “hot” and “cold”. In general, hot data is classified as data that is accessed very frequently and needs to be highly durable and available. On the other hand, cool data is data that is infrequently accessed and long-lived. Cool data can tolerate a slightly lower availability, but still requires high durability and similar time to access and throughput characteristics as hot data. For cool data, slightly lower availability SLA and higher access costs are acceptable tradeoffs for much lower storage costs. Azure Blob storage now addresses this need for differentiated storage tiers for data with different access patterns and pricing model. So you can now choose between Cool and Hot access tiers to store your less frequently accessed cool data at a lower storage cost, and store more frequently accessed hot data at a lower access cost. The Access Tier attribute of hot or cold is set at an account level and applies to all objects in that account. So if you want to have both a hot access tier and a cold access tier, you will need two accounts. If there is a change in the usage pattern of your data, you can also switch between these access tiers at any time.
It looks like there shouldn’t be a performance difference between the two; it’s more of a cost difference in which you might be able to save money by choosing your tier wisely.