A Hel will save you 23 points.
The value of the Eld will depend on the class of char that is using it.
A Paladin, clvl 85, with a plain SS needs 181 Dex for max block.
A Paladin, clvl 85, with an Elded SS needs 167 Dex for max block, only saving 14.
A Sorceress, clvl 85, with a plain SS needs 206 Dex for max block.
A Sorceress, clvl 85, with an Elded SS needs 188 Dex for max block, saving 18.
The difference is that sorcs get worse block naturally, so a flat 7% is a bigger proportional improvement.
Likewise, a Pally using Holy Shield will get even less benefit from an Eld. Similarly, increasing blocking with GA or a Safety amulet etc will also reduce the benefit from an Eld.
Hel wins, in every situation I can think of.
Even the most extreme case, a level 99 sorc with no other bonuses to blocking, the Eld only saves 21 (237 compared to 216).