The space egg actually ain't a bad lead even for frontliners because the nanites are a pretty good counter against capital ships and SB rushes...also, the extra constructor from its colonization can be invaluable in certain circumstances if you get to a choke point right before the enemy...
But otherwise, I'd agree that sovas or halcyons are going to be better than the colony cap...even as Vasari, skirantra is probably best 1st pick for frontliners and certainly the best 2nd pick if you lead with a space egg...
If you're in suicide, some would argue that a colony cap is better because you can use it to find a new HW near the map's center, but that is debatable and honestly I think it matters on how the teams are stacked...and expert player in suicide probably can keep two mediocre players busy long enough to justify bunkering down instead of sending the colony cap off to relocate the HW...