To answer the question, if you can make 400 a day with 2 men I would forget WFP and stick to your existing round. Thats good going. I presume its a full round.
WFP is quicker on an average round. You have an initial outlay, and its ongoing cost is more. I was doing pretty well trad and made the wfp jump. Turnover is now a bit more, net profit the same allowing for inflation.