Which would you be more concerned about ingesting - radioactive iodine or U-238? Why
Definitely the I-131. This has a shorter half-life (8.30 days) and is a Beta emitter than U-238 (4.5 billion years) and is an Alpha emitter. The shorter half life means it has a higher emission rate and overall activity. Beta radiation (electrons) also have a greater penetration than alpha radiation (He atoms).
According to http://en.wikipedia.org/wiki/I-131, the following ...
The health effects of I-131 and U-238 are discussed.