I would, without a doubt, recommend a high quality (but low cost) boar brush. Get started right with a natural bristle brush that will link you to the best of the wet-shaving tradition.
Do boar brushes take a little break in? To be sure. That's part of the experience.
The onerousness of the break-in process is often (to my mind) highly exaggerated on forums such as this one.
The somewhat smaller Omega 10066 or 10081 are good choices, as are the somewhat larger options in the Professional series such as the Omega 10068 or 10069, or the Proraso Professional (Omega), or The Goodfellas' Smile Wild Hog (Omega), the last of which I have not tried myself.
The Zenith boar brushes are also outstanding and can be ordered via "Your Shaving" in Spain at a very nice price (with fast shipping). The plastic handled Zenith 80 is outstanding and under $10. I prefer the unbleached options, but will admit the break-in is a bit longer. The 80 also comes "bleached." Zenith has a whole range of brushes and the cost rises with fancier handles, but they are all reasonable and--if treated well--will last decades (if not a lifetime) and just get better and better.
Boar is outstanding for developing soft tips (as the ends split) AND maintaining "backbone" (meaning the brush doesn't go "floppy" when wet).
A shave brush has two main purposes. One is to create lather, the other is to lift up hair to help soften the beard prior to shaving while gently exfoliating the skin. Boar does both well. Ultra-plush synthetic brushes IMO fail on the second point in my limited experience trying them. Far too floppy for my taste. YMMV.