An Elemental Suit weighs about a ton. It is, however, not substantially larger than a human if you disregard the jumpjet/SRM section. Definately less than 3 meters, maybe 2.50.
Compared to a Terminator, it has a higher mobility (topspeed 32 km/h, Jumpjets) but most likely weaker weapons and armor (BT-weapons seem relatively weak in general).
The armament normally consist of a small laser (which can be replaced by a flamer, heavy machine gun or micro pulse laser), a small machinegun and 2 one-shot SRMs, in addition to a mechanical claw. It can withstand a hit from a medium laser, tough not much more.
A Terminator is about 3 meters large and relatively slow (no known topspeed, propably about 5 km/h.
Standard armament consists of a storm bolter (dual .75 AP/HE rockets) and a power fist. However, assault cannons and heavy flamers are also often used, and a back-mounted missile launcher is also available.
Terminator armor is known to be able to withstand hits from tank main guns and laser cannons with relative ease and is nearly impervious to most weapons, including the mentioned storm bolter.
Comparision of stom bolters to autocannons to assess weapons:
A small AC/2 has a caliber of 20-25 mm. Compared to that, a storm bolter has a caliber of 19mm.
This indicates that they are of roughly comparable power.
Given that BAs can withstand 3-4 salvoes from AC/2s, a similar amount of bolter fire should be able to wound or kill a BA.
However, a Terminator armor typically prooves to be impervious to such weapons, which most likely indicates far superior amor protection.
This is of course a pretty rough comparision - while an Autocannon fires hypersonic, non-explosive or AP-shells, the boltshell is both armor piercing and HE. However, since it seems that the difference is quite big (BA being vulnerable to ACs, Termiantors almost invulnerable to bolters) it is likels that the conclusion is still valid.
If my conclusions are correct, then a normally armed Terminator could kill an Elemental Battlearmor with his storm bolter, while the Elemental would have to be quite lucky to cause any damage at all. While the Elemental has far greater agility, the difference is not large enough to avoid the Terminators fire and there is no weak side in Terminator armor to exploit (some points have weaker armor, but this is not focussed on, say, the back).
Close combat won't really happen, and if it does the power fist is far more lethal than the claw of the elemental.
If the Terminator has access to special weaponery (specificall the assault gun and Cyclone Missile Launcher), the fight becomes even more uneven).
