its incredibly hard to tell because we dont know where he's heading yet. Manning could get selected by a team like the Chargers and immediately start, in which case he might be the better choice. TEs are really a crap-shoot with the exception of all of about 3 in the NFL, so locking up a long term top notch TE is a great idea, but if it doesnt pan out, you lose out on a lot better options in this draft.
Does your leagues draft take place, before, or after the NFL draft. If after, wait until then and I'm sure you'll get better and informed responses.