Transactional versus Dimensional model for file upload web application -- preferred approach?
It depends on your data, and how you want to store it and access it later to report off it. Your database itself doesn't need to be geared specifically to one or the other, rather you can have tables that are transactional, dimensional, or simultaneously both depending on your use case.
In general, if you're doing some sort of reporting off the data, then normalizing your data with dimensions is helpful for performance, flexibility, and maintenance. But a transactional table can still store references to dimensions to represent the &quot;facts&quot; / qualitative portion of the data to maintain normalization. Or they can even directly store the dimensions inside them themselves, albeit being a denormalized representation of the data from the former.
See the following for two different schemas representing a transactional table that stores dimensions vs being normalized and storing references to those dimensions (T-SQL syntax):
Denormalized
CREATE TABLE DenormalizedTransactions AS
(
    TransactionId BIGINT,
    ItemName VARCHAR(100),
    ItemType VARCHAR(25)
    Quantity INT
);

Normalized
CREATE TABLE NormalizedTransactions AS
(
    TransactionId BIGINT,
    ItemId INT,
    ItemTypeId INT
    Quantity INT
);

CREATE TABLE Items AS
(
    ItemId INT,
    ItemName VARCHAR(100),
    Description VARCHAR(1000)
);

CREATE TABLE ItemTypes AS
(
    ItemTypeId INT,
    ItemType VARCHAR(25)
);