Another divergent marine chapter codex is about to be released, and poor Codex Space Marines are left wondering why they are still following the teachings of that hack Guiliman. It seams that when you break the rules you get some pretty cool toys.
I don't think that the other marine codecies are more than marginally better than stock Astartes, but their specialization lends to more competitive 5th edition armies. Each chapter codex has a focus, and if your marine army shares that same focus, you loose nothing by switching codecies. Running divergent chapters should be a trade-off, not a boon. As it is, there is no appreciable loss from changing your light-mech Codex Marine army to Blood Angels. You get essentially the same stats and available units, and also gain the benefits of being a Blood Angel. The points are different, but not substantially so. The options are not vanilla vs chocolate vs strawberry; its vannilla vs choclate-vannilla swirl vs strawberry-vannilla swirl.
Compare troop options between Wolves, Blood Angels, and Ultras. For my Ultras I have to take ten men to get a special and heavy weapon. Most of the time those two weapons are mutually exclusive in their use. The other two chapters can take ten men and get two specials that can be used together. Essentially trading duality for redundancy. That seems like a fair trade, but it's not.
There's a lot of talk about duality in 40k and its benefits. I'd rather take a redundant single purpose unit than a unreliable dual purpose unit. The limited role of the single purpose unit can always be covered by another redundant single purpose unit that fills the opposite role. Those types of units are not lacking in the divergent chapter codex's.
On top of taking the unfair trade, the Wolves and Blood Angels also get their army wide rules. They only have to give up Combat Tactics( a situationally useful rule) in return. You've lost some codex marine traits in the process, but never anything that makes the choice remotely hard.
I think that the divergent chapters should not get the basic marine stat line by default. They should have one stat take a penalty with the according adjustment in cost. This makes being a codex marine mean something as they would have the best overall stats but the least specialized rules and equipment.
I think Wolves should get -1 to BS to all units except Long Fangs and the units that already have BS3. Wolves are primarily a melee army, and having them less capable at ranged combat balances all their CC abilities and units
For Blood Angels I'd like to see -2 to leadership across the whole list. This way they are little less dependable than marines, and their ability to occasionally become fearless mean a little more.
Maybe I'm being jealous of the Stormraven, Dread Knight, and Thunderwolves, but vanilla is a flavor! To be vanilla doesn't mean to be completely void of flavor. Codex Marines needs something to set it apart from all the other Marine chapters, and that is currently lacking in 5th edition.