If the query is "long" and you are accessing the results from multiple queries, then a temporary table is the better choice.

A view, in general, is just a short-cut for a select statement. If does not imply that the results are ever run and processed. If you use a view, the results will need to be regenerated each time it is used. Although subsequent runs of the view may be more efficient (say because the pages used by the view query are in cache), a temporary table actually stores the results.

In SQL Server, you can also use table variables ( declare @t table . . . ).

Using a temporary table (or table variable) within a single stored procedure would seem to have few implications in terms of security, simplicity, and column names. Security would be handled by access to the stored procedure. Column names are needed for either solution. Simplicity is hard to judge without more information, but nothing sticks out as being particularly complicated.

depends

A view must replicate the processing of your "long query" each time it is run, while a temp table stores the results.

so do you want to use more processing or more storage?

You can store some view values (persistent index) which could help on processing, but you don't provide enough info to really explore this.

If you are talking about just storing the data for the use within a single procedure call, then a temp table is the way to go.

I'd like to also mention that for temporary table,
You cannot refer to a TEMPORARY table more than once in the same query.

This make temp table inconvenient for the cases where you want to use self join on it.

It is really a situational and operation specific question and answer may vary depending on the requirements of the scenario. However, a small point that i would like to add is that if you are using a view to store results of a complex query, which are in turn used in operations of a GridView, then it can be troublesome to perform update operations on complex views. On the contrary, Temp Tables can suffice to this perfectly.

Again, There are scenario's where Views may be a better choice [ as in Multiple Database Servers if not handled properly] but it depends on what you want to do.

In general I would use a temporary table when I want to refer multiple times to the same table within a stored procedure, and a view when I want to use the table across different stored procedures.

A view does not persist the data (in principle): each time you reference the view SQL uses the logic from the view to access the original table. So you would not want to build a view on a view on a view, or use multiple references to a view that has complex logic.

A TEMPORARY table is visible only within the current session, and is dropped automatically when the session is closed. If you need to repeatedly obtain the same results of a complex query, a TEMPORARY table can improve performance by storing the intermediate results.

A VIEW persists across sessions. Pretty much like a query under the hood, every time a view is accessed, the SQL server regenerates the results from the base tables. Although a VIEW is slower in this sense, a VIEW ensures the results obtained are up-to-date.