I never played 3rd, but I've only played spearhead and it's fun. I know Seraphon had coalesced and starborne in 3rd, which were psychic themed and saurus/dino themed respectively.

I looked at their rules on wahapedia and I'm wondering what a psychic heavy Seraphon army would look like. A slann starmaster seems mandatory, but how many is too many and when is Kroak worth running. How many kroxigors and saurus do you run, if any, and how do you synergize with your mages? The psychic side of the army looks cooler to me (skink starpriest, starseer, and slann) but I don't know how the current spearhead boxes fit into a psychic heavy army.

The starmaster looks like an intimidating paint job but Vincey V said they're actually deceptively simple to paint with drybrushing and washes.