@peace123 as at least 3 people have said, buyers never pay their buying agent directly. Buyers' agents get paid by taking half of the typical 5-6% seller's agent's commission which comes from the seller. So take the buyer's agent out of the picture because you can choose whoever you want and they'll all be a $0 cost to you.
For your decision on a seller's agent, if I'm understanding correctly you're deciding between paying a guy 6% or paying Clever $3k+2.5% (the 2.5% being the portion that they pass on to the agent representing the buyer of your condo, which they cant offer you a discount on because they need to pay that to the buyer's agent).
If you sell for $150k, the 6% guy will cost you $9,000 and the $3k+2.5% company will cost you $6,750. Relative to buying/selling a house, this $2,250 difference is small change and personally I'd go with whichever agent you trust more and have more confidence in, even if it costs you $2,250 more. That's a small investment for the benefit of having someone knowledgeable/trustworthy.
Obviously if you sell for more or less than 150k the numbers will be a bit different but this is the basic idea. If you sell for 170k your 6% will be $10,200 and 3k+2.5% will be $7,250, so a difference of $2950 at most. Again, that's relatively small change in this transaction. Go with the guy you trust, especially if you don't want to put in time to learn all about the process.
ETA: if you're looking to get the best service possible and have an agent who's willing to go the extra mile for you I'm not sure if nickel and diming them over every half-percent is in your best interest. A half a percent off is gonna save you $700- 850 here. If you were taking about a half percent on a million dollar home then maybe, but selling a $140-170k home I wouldn't negotiate hard for another .5% or even 1%. I'm sure others might not agree but that's my feeling.