The stem side of the valve can effect flow. The new valves are heavier because they're more tuliped than the stock valves. While being heavier, they should flow a little better. Backcutting the valves w/a 30 degree cut next to the seat could show a modest improvement.
I have sure seen better looking hand porting as far as looks go, especially the exhaust side. That said, if the guy is supposed to know these heads, I'd give him the benefit of the doubt until I knew better. Truth is, looking at your ports and chambers doesn't tell me much because I'm not familiar w/the heads and what they're supposed to look like. So for that reason I'm withholding judgement. In the end it's what the engine performs like that will tell the story. Unfortunately there's no real way around this other than using a flow bench to compare before and after- but even then I have seen less-than-stellar flow numbers that run very good, and good numbers that don't perform as expected.
At this stage, swap out the valves if you feel there's something to be gained in performance/€.
If you could, post a photo of a piston. I'm wondering how much of a quench effect they'll give w/your chambers. Even when it looks like there's not that much flat area, tightening the piston to chamber clearance (within safe limits) can induce turbulence that'll help reduce the tendency to detonate. Your heads do look to have useable quench areas, though. This is if you have a selection of head gasket thickness to choose from. If not, you're basically left w/whatever the clearance is.