Just note that the big advantage of binding is that you can have more than one spirit in existence at a time. With summoning, you're limited to only one.
The problem with Ally Spirits is that 5E has made them, IMO, a lot more difficult than necessary. You have to Initiate into the Invocation Art to get access to the Ritual in question. On the plus side, you can pair that initiation with a low-level Ally Spirit Conjuration as an ordeal, although it would ulimately involve more karma than just the straight initiation.
ETA: OMG, I just realized how ridiculous Terrance would be as an Ally Spirit, even at Force 1.
An ally’s Physical and Astral attributes equal its Force. However, allies start with an Edge attribute equal to the Edge of its conjurer.
With that said, being an aspected summoner, you lose out on a lot of the utility of an ally spirit. No spellcasting, so Aid Sorcery is useless, plus it means your spirit can't cast spells, which they otherwise could potentially do.
If you went super bare bones, it would basically cost you about 20 karma for the Initiation & F1 Ally Spirit Summoning combo. The shitty part is that I don't think you would get a metamagic. I'm not sure on that part of the rules, to be honest.