Transformer vs SMPS for bench supply
Mains (low) frequency transformer first is the old school way. Depending on the application, the whole supply can be extremely simple to design as the transformer already provides isolation. It results in a heavier unit because of the mains frequency transformer and unit cost is higher.

A switching PFC is the modern day way. It involves significantly more design (usually 2 switching stages), but it's better in terms of the aspects discussed above. Also the PFC stage shapes the current drawn from the mains plug, making it that of a resistive load. I'm not familiar with the regulations with regards to this, but you may not be allowed to go above a certain power level without doing something for the current to look good (PFC).

I guess I'd choose based on:


Power level (nominal and peak). If it's high, the transformer can be massive and also you don't want to draw current that's not PF correct.
How many units will be made, as to me there's a trade-off between development cost and unit cost.


I understand I'm not providing a definitive answer here, but hopefully I'm helping you get a view of some factors involved.