Let's compare! All boost and +1 for 1 resource. All are Assets that need to be played, generally costing 1 action.
Physical Training 2 resources to play, icons
Physical Training (2) 2 XP, 0 resources to play, icons
This card is 4 XP, costs 2 resources to play, icons, and gets 2 recurring resources for boosting.
- They all boost things most Guardians want boosted; while they tend to have 4-5 , there are a lot of enemies with difficulties that high, so pumping is nice. Similarly, Guardians tend to have 3-4 and there are a lot of 4-5 Treacheries.
- For the level 2 and 4 versions,resources are turned into bonuses immediately.
- Recurring resources are great; there will rarely be a turn where playing them won't help, and they can preserve using cards for icons, since Guardian tends to have sort of weak card draw.
- Levels 2 and 4 combo well with Well Prepared.
- They are slotless Assets, something that slot-starved Guardians will appreciate.
- Lots of Assets protect Guardians from Treacheries like Crypt Chill and Corrosion. That's not a happy use, but better to lose your booster rather than your weapon while you are engaged....
- They aren't permanent.
- They don't help with Guardians' really weak and .
- They are expensive to run, and Guardians have weak economies, although the Nathaniel Cho deck has offered some alternatives, and Big Money Leo is a thing.
- They are expensive, and Guardians already have a lot of other Assets to spend XP and resources on.
In general, if you want to "pay to pass," all of these are decent cards and give a clear progression to build up to the Level-4 version, which is definitely the best of the lot, assuming you have the XP to spare.
TL;DR AH:TCG is a land of contrasts, and some deck styles and play preferences will like these and others won't.