docs: provide recommendation for strategies (#3531)

* docs: provide recommendation for strategies

Signed-off-by: Kostis (Codefresh) <39800303+kostis-codefresh@users.noreply.github.com>

* docs: traffic manager clarifications

Signed-off-by: Kostis (Codefresh) <39800303+kostis-codefresh@users.noreply.github.com>

* docs: explain canary with/out traffic manager

Signed-off-by: Kostis (Codefresh) <39800303+kostis-codefresh@users.noreply.github.com>

* docs: add 3 columns on the comparison table

Signed-off-by: Kostis (Codefresh) <39800303+kostis-codefresh@users.noreply.github.com>

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Signed-off-by: Kostis (Codefresh) <39800303+kostis-codefresh@users.noreply.github.com>

docs/concepts.md

@@ -46,4 +46,33 @@ A Canary deployment exposes a subset of users to the new version of the applicat
 [![How Canary deployments work](concepts-assets/canary-deployments.png)](concepts-assets/canary-deployments.png)
 
 The picture above shows a canary with two stages (10% and 33% of traffic goes to new version) but this is just an example. With Argo Rollouts you can define the exact number of stages
-and percentages of traffic according to your use case.
+and percentages of traffic according to your use case.
+
+## Which strategy to choose
+
+In general Blue/Green is the easier strategy to start with, but also the more limited. We recommend you start with Blue/Green deployments first and as you gain confidence for your metrics and applications switch to Canaries.
+
+You also need to examine if your application can handle canaries or not.
+
+* Blue/Green always works because only one application is active at a time. Not all applications can have different versions running in parallel at the same time (which is what canaries are doing). This can be a showstopper for adopting canary deployments especially for legacy applications.
+* Blue/Green is simpler because you can get their full value WITHOUT a traffic manager. While canaries can also work without a traffic manager, most of their advanced features assume a fine-grained way to control traffic. If you don't have a traffic manager, then you can easily get the full value
+of blue/green deployments but only the basic capabilities of canaries.
+* Blue/Green also works with services that use queues and databases (workers that fetch tasks). Argo Rollouts doesn't control traffic flow for
+connections it doesn't understand (i.e. binary/queue channels).
+
+Here is a summary table for the possible approaches.
+
+|                           |         Blue/Green        |       Basic Canary         | Canary with Traffic manager    |
+|--------------------------:|:-------------------------:|:--------------------------:| :-----------------------------:|
+|       Adoption Complexity |           Low             |       Medium               |        High                    |
+|        Flexibility        |           Low             |        High                |        Maximum                 |
+|    Needs traffic provider |                 No        |         No                 |           Yes                  | 
+|  Works with queue workers |                Yes        |         No                 |            No                  |
+|  Works with shared/locked resources | Yes             |         No                 |            No                  |
+|            Traffic switch |     All or nothing        |  Gradual percentage        |      Gradual percentage        |
+|           Traffic control |     0% or 100%            |  coarse grained            |     fine grained               |
+|       Traffic depends on  |     deployment state      |  number of canary pods     |     Any split option is possible                |
+| Advanced routing scenarios |         No               |       No                   |         Yes                    |
+|      Failure Blast Radius | Massive impact            |  Low impact                       | Low impact              |
+
+Note that that traffic manager can be any compatible Service Mesh or Ingress Controller or Gateway API implementation (via a plugin).