Besides the obvious Shields uses defense and Elec mainly focuses on resists there's a lot of key differences between the two armor sets that make them both interesting to play, depending on what sort of goals you want your scrapper to accomplish.
First elec now (finally!) has a self heal and has its own global recharge power 20% global all the time. If you want good survivability with resists (which mitigates damage by reducing the amount of damage you take ) and being able to use powers more often. Elec is great. Also Elec also is very good if you want something that doesn't want to run of endurance. Power Sink and its self heal both help this. Elec is good, what meshes with it well? That is for you to decide.
Comparing Elec to shields the two sets are very very different. Shields can be a monster because it has the ability to soft-cap defense (with a healthy amount of money investment), and has a power that can give you (with the right number of mobs around) constant buildup as far as a damage bonus is concerned. The set can have some end usage problems and DM shields is a very popular soloing build (all around build as well, but I believe soloing AVs is what this build goes for, as well as fire/shields)
As far as being better off with one or the other it totally depends on your playstyle, what you're looking for in sets and what you want to accomplish. I've provided some basic info so I hope you can make a decision from that.
In the Grand scheme of things people don't know when to shut up.
Elprede- 50 Blaster Ice/elec
Flaron Llothren- 50 Tank Ice/SS
Technic Flame- 50 Controller Fire/kin
Lance Indalen- Brute 50 Em/elec
Heart widow- Widow 50
Elec Armor:
- damage aura, some people say you can do good end draining slotting it for endmod, I personally haven't tried and think it's a waste
- resistance based set and you'll probably cap your energy resistance with SOs at 22
- 20% rech bonus + runspeed + slow resist on l. reflexes (just like quickness from /SR)
- psionic resistance on the mez shield (so, great against Rikti with the nrg and psi resists)
- end drain resistance in one of the shields and Grounded
- self heal (longish recharge timer tho) which boosts your regen and gives you an end discount for 30 secs.
- Power Sink for never having to worry about end after 35
- lackluster tier 9 because scrapper resists cap at 75% and not 90% like Brutes/Tankers, with a harsh crash like Unstoppable and a tiny-radius EMP Pulse at the crash.
- knockback hole when you're jumping/airborne or sometimes even standing on the floor when it's not perfectly flat (I use a steadfast -KB IO on grounded because of this)
- tight build depending on primary, difficult to get everything you want at the 'right' levels like if you want your travel at 14 and stamina at 20, you may have to delay grounded or some other nice power. I skipped the travel power b/c of Ninja Run + Hurdle + L. Reflexes and it works great. Oh and you'll want Tough too.
Shields:
- +max HP/resistance power
- a little bit of resistance against all but psi
- hard to cap defenses because of lower def numbers than SR
- aggro aura that boosts your damage and lets you hold aggro like invul so you can be a mini tank, especially with over 35% defenses
- telenuke (shield charge), some people think /shields is overpowered because of this
- Defense Debuff Resistance that can get to 95% on high recharge IO builds
- no self heal (with DM, siphon life makes up for that) and no +end power (Physical perfection can help a lot)
- mez resistance to EVERYTHING
- perhaps the best build with a 2billion+ investment, I haven't played a Shields toon yet but some people say it feels rather squishy while leveling because of low def numbers.
- if you look at the Rikti pylon results thread, which measures single target damage, all the top guys are /shields because of the +dmg taunt aura.
Well hope I didn't forget anything, I'm on Mac OS X so no Mid's to check the powers accurately, don't feel like booting to Windows XP just for that 
Im looking to make another scrapper but having a problem deciding between a DM/Shield or ?/electric armor. Ive never tried electric armor so i dont know the pros and cons to it. What meshes well with electric? Is electric any good, or am i better off with a DM shield? Thanks!