Take a third option for open-world Sandbox RPGs, take a break from Bethesda, and get Two Worlds (The first one):
Yeah, the dialogue/voice acting sucks in that game (But can be absolutely hilarious: "Reminds me of my in-laws!"), and it has poor character creation, but...
Mounted combat: Somewhat difficult to learn, but rewarding when you adjust to it.
Unlike Oblivion, it has spears.
The loot system is far superior to Oblivion or Fallout 3's... Oblivion had approximatel two or three dozen unique armor sets. Two Worlds has several hundred complete armor sets. It also has a superior system for customizing and upgrading equipment to match your playing style and aesthetic sense, due to the "Gear Melding" mechanic: No, it's not logical or realistic, but it's certainly fun and rewarding: Like the sword you find, then find a better one you don't like the appearance of? Sell the "better" one and improve the old one until it'ss stronger. Or, if you have a good weapon, you don't have to wait forever before hope of getting an upgrade comes along.
The landscape is absolutely massive, with more unique environments than Oblivion and Fallout 3 put together.
The level scaling isn't quite as painful as it is in Oblivion or Fallout, to the point of almost mistaking it for being non-existent because the way the character outpaces threats (In Oblivion, the character starts out stronger than everything, then the monsters get stupidly stronger than him unless you practice "Efficient Leveling" (Generally, as soon as Bears and Will-o-wisps appear on the Leveled Monster Tables), then becomes a cakewalk the further you get from level 20. In Two Worlds, you start out weak compared to everything, and have to fight cautiously, but your power gradually grows to Demi-God levels (Albeit still too fast for some.)
Honestly, if Two Worlds had managed to get a modding community as good as The Elder Scrolls, it would have been the better game; a shame its marketers don't know how to do anything but sling mud and superfluously boast about its own qualities...