I would agree with
@DustyBin, the F-16 is probably still the better bet. Firstly the training requirements will be less for a single seat jet as the twin-seat F-15Es would require the training of the weapon system operator of which the Ukrainian Air Force will only have a handful already (the only twin-seat fast jets they operate are Su-24 Fencers, and they only had a handful before the war) so to be effective they'd have to train from scratch a load of new weapon system operators. Or you could give them single seat F-16s and their entire cadre of existing fast jet pilots (thought probably not all at the same time!) can do conversion courses to F-16s which I would wager would be considerably quicker than having to learn a new role from scratch! I'm also not sure if the Ukrainian's want a bomb truck (which isn't to diminish the F-15E's air superiority capabilities because they are prodigious, but it is primarily a strike fighter) rather than something which is perhaps better suited to doing a bit of everything quite well.
But the main thing for me is, again, numbers and logistics. There are thousands of F-16s including significant numbers of stored airframes in the US as well as hundreds within European NATO many of which are still frontline operational but quite a number of which are either about to be retired or have recently been retired. That means that the airframes are available in significant quantities (far more than Ukraine could probably ever hope to operate) but that also the logistics are already in place in Europe. There are the spare parts, the repair facilities, the training opportunities for mechanics, etc etc.
The F-15E only had a production run measured in the hundreds, none of them are operated by European nations and the USAF only operates a handful of them based in the UK. They aren't going to be available in significant numbers and the logistics are that much trickier as the closest place that might have spares or ability to effect repairs of damaged/worn components is all the way back in the UK. Unlike the F-16 which is operated by the Polish Air Force right next door to Ukraine.
Though this all presupposes that jets will be forthcoming at all. It's taken an achingly long time to get around to supplying MBTs (and even then the numbers are still not what I'd like to see personally!). Whilst I hope that it won't take as long to get to the point where we start making jets available I still can't help but feel we're going to be waiting some time...