Data modelling - from source or DAX

Hi all, 

New to BI - trying to work out best approach for the following scenario. 

My main metrics table in report includes metrics such as:

Pick travel time - it uses a date time stamp to compare the previous row (LAG) to the current time stamp

CASE WHEN LAG(AL.TaskDetail_ACTION_DATE_TIME) OVER (PARTITION BY AH.TaskHeader_REFERENCE ORDER BY TaskDetail_ACTION_DATE_TIME) IS  NULL THEN
		DATEDIFF(SECOND, AH.TaskHeader_START_DATE_TIME, AL.TaskDetail_ACTION_DATE_TIME)
ELSE 
		DATEDIFF(SECOND, LAG(AL.TaskDetail_ACTION_DATE_TIME) OVER (PARTITION BY AH.TaskHeader_REFERENCE ORDER BY TaskDetail_ACTION_DATE_TIME),
							AL.TaskDetail_ACTION_DATE_TIME) 
END AS [Seconds To Pick],

It also includes a calculated "travel type category" e.g. changed ailse, first pick, same location, changed level (there's currently 8 categories)

My question - should i be:

1. creating a "travel type category sql view" (with an unknown for accidental additions in the future that aren't catered for), OR

2. creating a "travel type category " table in power bi (DAX) 

3. simply return the value in my metrics table and don't worrry about creating a 'dimension' at all (my value is good enough - i don't think i need an addition description column or anything in my dimension)

I'm sure it depends - but what is best practice (generally 🙂 )

I'm guessing number 1 the sql view is best but has the issue of always keeping travel cats and in metrics table and travel cats view in sync?

But i'm not sure either - my (limited) understanding of vertipaq is that it's very good at grouping a column with low cardinality.

Thanks for any assistance.

Clay

 table