Lurker comment:
Concerning infiltration, I think it is by all means superior to anything else at this stage of game.
You'll get around 3,5k EPs. You just can't generate that many EPs in reasonable time at this point. The downside is getting EPs only towards one rival, so you'd have to choose carefully.
Infiltration is a huge chunk of EPs no doubt (I thought it was a bit less than 3.5k though). The downside is that there is a lot of time between now and when you can reasonably use the EPs. It is very different from lightbulbing which gives you an immediate tech.
To get the benefit of EPs, it takes time. You have to:
-Figure out who to infiltrate: Monty is close, but not a tech monster. Since it is a huge decision, waiting to decide who to infiltrate usually makes sense.
-Build sufficient spies to infiltrate (this is a royal pain, especially when you would like to be building units for an aggressive neighbor).
-transport spies to the target CIV and wait for the 5 turns to pass.
-Succeed at tech stealing.
-repeat.
All of that time allows the benefits from Scotland Yard to accumulate to a fairly decent pool of EPs. For example, if SY adds 10EPs and it takes you 50 turns before you start stealing, SY has added 500EPs.
Admittedly, this is no where near the infiltration EPs, but it is usually enough to steal all or at least most of what you want to steal. In a commerce high capital (you guys need more workers/cottages

I'm not saying that SY is necessarily better, but I don't think infiltration is a no-brainer. In the right circumstances (commerce high capital, unclear infiltration target, etc), SY can be very strong.
On the downside, you have pretty high costs right now (from city maintenance), which will mean you can't run the EP slider as high. This puts a crimp in the benefit of SY.
Tough call...
GS